The Best Dish Soap

Dishwashing liquid, the kind you squirt into your sink to do dishes by hand, is something that most of us have in our kitchens. After more than 65 hours of research, we think Seventh Generation Dish Liquid is the one you want. Out of the 28 different hand dishwashing detergents we lab tested, it has the best combination of cleaning power, safety, price, and social responsibility. It also smells good, if that’s your thing, and comes unscented if it isn’t.

Seventh Generation Dish Liquid
You can’t beat the cleaning power of Seventh Generation. Bonus: It’s cheap, skips the fragrances, and isn’t tested on animals.

*At the time of publishing, the price was $16.

Also Great

*At the time of publishing, the price was $14.

Dawn Ultra Original Scent Dishwashing Liquid
Just as great at cleaning as Seventh Generation, but doesn’t come with a smell-free option. It’s more widely available, but they also test on animals.
Dawn Ultra is excellent at cleaning, too, and a good pick if you don’t mind fragrances or animal testing. Both it and the Seventh Generation are safe, reasonably priced, and will get the job done better than the rest.

Table of contents

Why you should trust us

For this guide, we read every available review of dish liquid—including those from Consumer Reports, Good Housekeeping, Real Simple, America’s Test Kitchen, and Grist—and ingredient reviews from sources such as GoodGuide and the Environmental Working Group (which are flawed, but we still read them). We also talked to professor Brian Grady, a surfactant expert and director of the Institute for Applied Surfactant Research at the University of Oklahoma; professor Jennifer Field, an environmental and molecular toxicologist at Oregon State University; and Cara Bondi, the Research and Development manager at Seventh Generation.

As for me, I’m a chemistry Ph.D. who has a weird obsession with soap and explaining the chemistry of everyday cleaning supplies, like detergents.

How we picked

The primary job of a dish detergent is to get oil and grease off your dishes. Almost all dish liquids on the market can do this to varying degrees—it’s the degrees that matter. You might also be looking for a detergent that has a minimum of worrisome ingredients and is easier on your conscience.

There are a fair number of dish detergent guides out there, but there are no great ones. Consumer Reports says that all detergents they tested will get your dishes clean and recommends Ajax because it works well and is cheap. Publications such as Good Housekeeping, America’s Test Kitchen, and Grist compared how well different detergents scrubbed off caked-on grease and food. However, it’s extremely difficult to bake the exact same amount of grease on a number of pans and also make sure you use the same amount of force to scrub it off. In addition, both Good Housekeeping and Grist only looked at “green” detergents, not any conventional ones. Plus, they also gave points for how well dish soaps foamed, but that’s not an indicator of how well a detergent can clean (as we explain below).

There are also some ingredient guides out there, such as the Environmental Working Group (EWG)’s Guide to Healthy Cleaning, and GoodGuide, which are both less than ideal. The EWG often does not give specific reasons for its ratings. For example, they will say things such as “May contain ingredients with potential for respiratory effects; acute aquatic toxicity; cancer,” but do not say what the concerning ingredients are. In addition, they don’t list any sources or link to data. GoodGuide does a better job of breaking down ingredients, but their sources are not great (mostly Wikipedia). Neither outlet tests to see which product works the best. Lacking a good, comprehensive guide, we decided to do our own tests.

Lacking a good, comprehensive guide, we decided to do our own tests.
To figure out which ones to test, we looked at the bestsellers at Amazonthe top scorers at GoodGuide; ones that topped the testing charts at Consumer Reports, Good Housekeeping, Real Simple, America’s Test Kitchen (aka Cook’s Illustrated) and Grist; and some been-around-for-ages brands that our moms and grandmas used. We took conventional detergents and some “green” detergents with fewer ingredients that some people are concerned about. We also made sure to include a few “free and clear” varieties that don’t have dye or fragrance added. We ended up selecting 20 dish liquids for our first round of testing:

Ajax Super Degreaser Dish Liquid, Lemon.  A best buy from Consumer Reports.

Better Life Dish It Out. Shot up Amazon’s bestseller list, presumably because it was featured on the TV show Shark Tank. This one doesn’t have any of the common cleaning agents that some people are concerned about, and we wanted to see how these compare to more traditional dish liquids.

Biokleen. A common green dish liquid that some people love and some think is awful. We wanted to form our own opinions.

CitraSolv. This was a bit of a personal pick. I use the brand’s all-purpose cleaner and love it. Was curious about the dish liquid.

Dawn Direct Foam Fresh Rapids. Winner of Consumer Reports’s tests.

Dawn Platinum Power Clean. Recommended by Real Simple. They call it the dish liquid with the most muscle.

Dawn Ultra Dishwashing Liquid, Original Scent, Blue. The classic Dawn, and number one on Amazon’s bestseller list for dish liquids. Also recommended by Cook’s Illustrated.

Dawn Ultra Pure Essentials Dishwashing Liquid. The version of above without dyes. Wanted to see how it compared with the classic stuff.

Eco-me. Recommended by and bestseller at Gimme the Good Stuff, another without common cleaning agents.

Ecover Natural Dishwashing Liquid. One of the top-selling green brands at Amazon, plus it was Grist’s pick and Consumer Reports’s green pick.

GrabGreen in Red Pear with Magnolia. This and Cucina in Coriander and Olive Tree (which we tested in another scent in our recent update) were in a tie for best fragrance from Real Simple.

Ivory Ultra Classic Scent. Cook’s Illustrated recommended.

Joy Ultra Concentrated. Cook’s Illustrated recommended.

Method in Clementine. Method offers refills, so you don’t have to buy a whole new bottle when you want more. And Clementine seemed to be the most popular scent, so that’s what we went with.

Mrs. Meyer’s Clean Day Dish Soap, Lemon Verbena scent. Ditto on the cult following for fragrance on this one, plus it’s also a popular green dish liquid.

Original Palmolive Ultra. The classic for no more dishpan hands! Thanks, Madge. Plus, recommended by Cook’s Illustrated.

Palmolive OxyPlus. Version of above but with OxyClean, a bleach alternative. Wanted to see how it compared to the regular version.

Planet Ultra. Good Housekeeping pick for green dish liquids, and on the top of GoodGuide’s list

Seventh Generation Dish Liquid. The number one bestselling green dish liquid according to Amazon, and a strong number three overall. Also highly recommended by Cook’s Illustrated, and Real Simple’s pick for gentlest on skin.

Up & Up fresh scent (Target store brand). We wanted to test a generic brand along with the others, and this is what I had in my cabinet. Plus it says on the bottle, “Compare to Dawn Ultra!” So we did.

Some of the dish liquids that we tested. Photo by Alex Farris

Some of the dish liquids that we tested. Photo by Alex Farris

For our latest update, we added eight more soaps to the mix:

Seventh Generation Ultra Power Plus, their new offering. We wanted to see how it measured up to our top pick.

Costco’s Kirkland Eco Friendly Liquid Dish Soap. Consumer Reports liked this one, plus a lot of readers requested that we test it. We aim to please.

Cucina dish detergent. This got four stars from Good Housekeeping, and it gets very good Amazon reviews.

Caldrea Dish Soap. Good Housekeeping gave Caldrea four stars, and GoodGuide likes it as well. Amazon users also rave about it.

Ecos/Earth Friendly Products DishmateGoodGuide liked this one, and while Consumer Reports tested it, at the time of this writing their ratings for dish liquids aren’t up on the site anymore, so we don’t really know what they thought.

Clorox Green Works. Another one that did well with GoodGuide.

Palmolive Ultra Soft Touch with Vitamin E. Good Housekeeping gave this high ratings, as did many Amazon users.

Puracy 100% Natural Liquid Dish Soap. Despite the blatant BS in the name of this detergent (there is no such thing as a 100 percent natural dish soap—soap does not spontaneously occur by itself in nature), people on Amazon loooooooove this stuff. Almost 500 reviews at the time of this writing. Holy schnikies.

We did not test any dish liquids that were labeled as antibacterial. We go into more detail below about why, but, in short, the FDA isn’t sure that antibacterial ingredients such as triclosan actually get rid of germs, and they might be hurting our health. We also didn’t test the different fragrances of the same type of detergent, since we assumed that these would have the same basic formula, and therefore performance. (Fragrances don’t have any role in the chemistry that gets our dishes clean.) One exception to this was comparing Original Dawn to Dawn Pure Essentials, since they have slightly different formulas. We also didn’t test a Dawn non-ultra variety, since the company’s PR person told me that they “weren’t supporting the brand” any more, and you can only get them at Dollar General stores (although you can still get it at Amazon at the time of this writing).

How we tested

When setting up a testing method, we ran into two problems. As mentioned above, it’s difficult to bake on a set amount of grease to a dish or pan. Second, short of building a scrubbing robot, it’s also hard to wash a dish with the same amount of pressure and strokes each time. So that makes the most obvious test—just washing some dirty dishes—not really work. Instead, we listened to surfactant expert Grady.

Brushing the oil/food coloring mixture onto the plate. Purple gave the best contrast. Photo by Alex Farris

Brushing the oil/food coloring mixture onto the plate. Purple gave the best contrast. Photo by Alex Farris

The less oil remaining on the plate, the better the detergent is at cleaning.
We took some vegetable oil, mixed in some oil-soluble food coloring, and brushed a thin layer on a plate. We let this sit for 5 minutes, then placed two oil-coated dishes in the bottom of a tub containing 5 milliliters of detergent and 10 liters of approximately 70°F water. We made sure to add the detergent after the tub was filled and mixed gently to discourage foaming. We beat the mixture with a handheld egg beater for 2 minutes to agitate the surfactants in the detergent. Surfactants, short for surface active agents, are the soap-like molecules in cleaning products that bind oil and water together so they can be washed away. (For more details on how, see our explainer below.) Then we pulled the dish out, lay it flat, and eyeballed how much oil was remaining on the plates. Finally, we took the cleaner plate (in most cases the two plates were virtually identical) and compared it to the control.1 The less oil remaining on the plate, the better the detergent is at cleaning.

Agitating the water with an egg beater in one of the tests. Photo by Alex Farris

Agitating the water with an egg beater in one of the tests. Photo by Alex Farris

This method works in a couple of ways. It measures how the detergent by itself can work to clean away oil, which is the point of a dish detergent. It also leaves out the scrubbing factor, which might make people think that their detergent is working harder than it is. Because really, if you scrub hard enough with any detergent, your dish will come clean. However, since we were eyeballing the remaining oil and not using a machine to tell us precisely how much food coloring was left behind, we had to put the detergents into relative categories. These were excellent (5-10 percent oil remaining), very very good (10-15 percent oil left), very good (15 percent), good (20 percent), okay (25 percent), and poor (35 percent). For reference, the control had about 40 percent of the oil left on the plate.

Our pick

Seventh Generation Dish Liquid
You can’t beat the cleaning power of Seventh Generation. Bonus: It’s cheap, skips the fragrances, and isn’t tested on animals.

*At the time of publishing, the price was $16.

There were two clear winners in the cleaning tests: Seventh Generation and Dawn. Both of these detergents topped the pack and were determined equally excellent. That said, Seventh Generation is our ultimate pick because the company doesn’t use dyes in its product or use synthetic fragrances (to learn why you might want to avoid these, see Are “green” detergents really better? and Other ingredients of concern, below), and it doesn’t test on animals.

Flaws but not dealbreakers

None. This detergent is made from angel tears.

Seriously, this stuff is great, comes in some nice scents if you’re into that, is available almost everywhere, and is very reasonably priced (in stores, at least—it tends to be more expensive online, for whatever reason).

Runner-up

Also Great

*At the time of publishing, the price was $14.

Dawn Ultra Original Scent Dishwashing Liquid
Just as great at cleaning as Seventh Generation, but doesn’t come with a smell-free option. It’s more widely available, but they also test on animals.
But Dawn works great, too. Seriously. And it’s also reasonably priced. Depending on what your priorities are (remember that Seventh Generation, our top pick, is not tested on animals), either is a great choice.

In our recent update, Clorox Green Works did just as well as these top two. It might be a little harder to find in stores, however, so we stuck with our previous picks. But if you can find it, it’s a great choice.

The competition

The runners-up were not far behind. The following detergents fell into the Very, Very Good category: Dawn Ultra Pure Essentials Dishwashing Liquid (no dye),2 Joy Ultra Concentrated, Planet Ultra, CitraSolv, and Dawn Direct Foam. In our update testing, Cucina, Seventh Generation Ultra, Kirkland, and the Palmolive with Vitamin E placed here too. These were also good cleaners, and you honestly probably couldn’t go wrong with any of these either, especially if one has a scent that you particularly love. (Personally, I kind of want to spread the CitraSolv behind my ears for perfume.) I should note that to me, the Kirkland smelled awful. My 3.5-year-old was watching me test for the update, and he noted that, “This one makes stinky water!” YMMV. The Dawn Direct Foam also deserves a special mention because it’s meant to be applied directly to your sponge instead of squirted in the water. We tried doing some oily dishes this way too, and the foam actually lasted quite a while. As a result, you could potentially use A LOT less water if you do your dishes with this.

Pulling plates out of the Ivory testing bath. Photo by Alex Farris

Pulling plates out of the Ivory testing bath. Photo by Alex Farris

The rest of the detergents fell into the middle of the pack. However, we should mention that both Biokleen and Puracy fell into the Poor category. About 35 percent of the oil was still on the plates washed with both of these. This is barely better than plain water, which had 40 percent of the oil left. (As my 3.5-year-old assistant said when I pulled out the Puracy plate, “This one is not done yet!”) So we would avoid both of these, unless you like dirty dishes.

How to do dishes

We tested dish liquids in room temperature water and put the detergent in the water after the sink was filled. (Remember, suds aren’t an indicator of cleaning power.3) Right about now, you may be wondering if you’ve been doing your dishes wrong for years. Don’t worry, you haven’t. We asked Grady-the-surfactant-man and both Dawn and Seventh Generation if there is a preferred way to do dishes. Grady says that which order you add detergent and water doesn’t really matter, as long as the detergent is mixed into the water well. “In theory less foam is better,” he says, “but the effect is so small as to be negligible.”4 But adding the detergent first does help with getting it evenly distributed. Grady says that he adds detergent just before turning off the tap. Soaking also helps, but about five minutes is long enough in most cases.

Both Dawn and Seventh Generation said that customers should do dishes in a way that works best for them, and that they don’t have any specific recommendations. So basically, you could do your dishes naked with sardines in your ears,5 as long as you use their product.

For doing dishes at home, temperature does not matter too much. Hot water will help dissolve grease better, but it won’t kill bacteria on your plates. According to the FDA rules for restaurants (PDF), to sanitize dishes,  you need the water to be around 171°F. That’s really hot.6 Most people can only stand water temperatures around 110°F, and most people keep their home hot water heaters set at around 135°F or so. So washing your dishes in really hot water at home won’t do much if you want to kill bacteria. For restaurants, the FDA requires that employees wash dishes in 110°F water, rinse well, then submerge the dishes for at least 30 seconds in a sanitizer solution. According to a study from a few years ago, washing your dishes in cooler water than 110°F will still kill bacteria, as long as you soak them in a sanitizer afterwards. Bleach works, and you don’t need much. A tablespoon in a gallon of water is the MAXIMUM that the FDA allows for surfaces that will touch food (PDF), and a teaspoon in a gallon of water is probably enough. Let dry completely before using the dishes, or rinse them off with clean water after sanitizing. But if you don’t want to use a sanitizer, you can minimize the amount of bacteria on your dishes by washing them as soon as possible after use. Bacteria tends to cling to the tines of forks and plastic dishes, so give these special attention.

Are “green” dish detergents really better?

According to some data gathered for us by environmental and molecular toxicologist Jennifer Field, the main surfactants in dish detergents, sodium lauryl sulfate (SLS) and sodium lauryl ethyl sulfate (SLES) (more about these here), both decompose in sewage treatment plants and soil (where your wastewater ends up if you have a septic system). In addition, once they’re in the soil, they don’t move to other places. As such, these compounds aren’t a hazard to the environment. However, dumping ANY soap directly into a water system is a bad idea, regardless of which surfactant is in the bottle. All of them will kill fish.

We go into more detail below, but dish detergents have little to no phosphate, a potential water pollutant these days. So that’s out as an environmental hazard.

It looks like one of the few differences between “green” detergents and conventional dish detergents is where their ingredients come from.
It looks like one of the few differences between “green” detergents and conventional dish detergents is where their ingredients come from. According to Cara Bondi, the Research and Development manager at Seventh Generation, their detergents only use ingredients that come from plants. Instead of cleaning agents that come from petrochemicals,7 their detergents are made from coconut and palm oil (sustainable palm oil, she said).8 Seventh Generation also does not use synthetic dyes, some of which don’t biodegrade (not to mention that dyes are a totally unnecessary ingredient.) Seventh Generation also does not use any Volatile Organic Compounds (VOCs), which can deteriorate air quality and lead to smog. Bondi says that all these things add up to a smaller carbon footprint for their detergents.

How much does this matter? Well, it’s unclear. We can’t find any scientific studies on the environmental impact of oil versus plant based detergents. Companies that sell “green” detergents say it does matter, but then they want to sell their detergents. According to the American Cleaning Institute, a group made up of companies that make cleaning products and their raw ingredients, there are environmental tradeoffs to using both renewable and non-renewable sources for cleaning products, so it tends to even out. They say that while plant-based cleaning agents “are derived from a renewable resource, they typically produce more air emissions and solid waste. Petrochemical surfactants, on the other hand, consume more total energy, since they are made from resources used as energy.” Unfortunately, they do not link to a source for this research.

Making this even more complicated is an interesting experiment run by Rebecca over at Green Baby Guide. In her quest to find the best dish detergent, she tested a number of different brands over a year in her kitchen. She found that with green detergents, she tended to have to use more to get her dishes clean. Because of this, she tended to use the bottle up faster, which created more plastic bottle waste and cost her more money. She found that based on how long it lasted, using Biokleen green dish detergent would cost her four times as much than the generic brand, and produce about six more empty bottles per year.

So is it worth it to buy “green” dish detergent? The answer is a bit hazy, but based on everything we could find, it’s unlikely to have much of an impact, if any at all.

However, there is one difference that may be important—“green” dish detergents tend not to test their products on animals. We don’t think this falls under an environmentally friendly heading per se, but we do consider it a plus. So that earns points for our ultimate top pick, Seventh Generation.

Surfactants and a potentially hazardous byproduct

There are two main surfactants that most companies put in their dish liquid, sodium lauryl sulfate (SLS) and sodium lauryl ethyl sulfate (SLES). As you can probably tell by their names, the two are very closely related. They have similar properties, too. SLS cleans a bit better and is foamier, but is also more likely to form soap scum and is more irritating to skin.9 SLES, also known as sodium laureth sulfate, is just SLS transformed into a compound that doesn’t cause soap scum. Chemists create SLES through a process called ethoxylation, which is basically just adding chemical fragments called ethoxy groups to the grease-loving part of the surfactant molecule. This makes the surfactant less likely to interact with the dissolved minerals in tap water, and hence produce less soap scum.

When you make SLES from SLS, the reaction creates a small amount of a compound called 1,4-dioxane. Manufacturers can remove this contaminant from surfactants through a process called vacuum stripping, but some can still make it into the finished bottle of detergent. And because it’s a contaminant and not an ingredient, detergent companies aren’t required to say on the label that it’s in there.

1,4-dioxane is described by the EPA as a probable human carcinogen. This means that there aren’t any definitive test on humans, but the compound has caused cancer in lab animals at high concentrations. Scientists also know that 1,4-dioxane can be absorbed through the skin, although it’s more likely to cause harm if it’s inhaled.

Now the important thing to remember here, and with all chemical exposure, is that the dose makes the poison. No compound is toxic in and of itself; how much a person is exposed to is what’s important. For example, the toxic dose of a chemical such as arsenic is much much lower than the toxic dose of a chemical such as water. But let’s get to the question that people are worried about.

Will 1,4-dioxane in dish detergent harm me?

Quick answer for those who don’t want to read this whole section: It’s incredibly unlikely.

And here’s why. According to the toxicological profile of 1,4-dioxane put out by the Agency for Toxic Substances and Disease Registry in 2012, the National Academy of Sciences says that polysorbate, a food additive, should not have more than 10 parts per million (ppm) for 1,4-dioxane. That’s 10 molecules of 1,4-dioxane per one million molecules of other stuff in polysorbate. The EPA says that drinking water with 4 ppm of 1,4-dioxane for a day or 0.4 ppm for 10 days is not expected to harm a child. The FDA has a limit of 10 ppm for 1,4-dioxane in the spermicide N-9 and also 10 ppm for compounds that end up in dietary supplements.

To sum up: It seems the popular limit for 1,4-dioxane is 10 ppm. And that’s for products that you ingest or otherwise put inside your body. There aren’t any guidelines for 1,4-dioxane levels in cosmetics or cleaning products right now, but the FDA has done some skin absorption studies on it. They found that 1,4-dioxane can be absorbed in the skin in certain cases, such as when it’s found in lotion. However, they found that the compound evaporates really fast, which means that a very small amount makes it into the skin, even when these products remain on the skin for hours. Add this to the fact that there’s a very small amount found in products such as lotions to begin with, and you get a very very small amount that might actually be absorbed.

In short: The FDA is not really worried about it. They are monitoring it though, and advise manufacturers on what they can do to minimize the amount of 1,4-dioxane in their products.

Let’s get back to dish detergent. Most conventional dish detergents, such as Dawn, Ajax, and the like, use both SLES and SLS in their detergent formulations. And most “green” detergents, such as Seventh Generation, Ecover, and Mrs. Meyer’s Clean Day, use only SLS. Remember, 1,4-dioxane is more likely to be in products that contain SLES. I chatted with Maia James over at Gimme the Good Stuff, who put together this safe product guide for dish detergents.  While the guide uses language that seems to imply there is a risk where there may not necessarily be, it’s pretty extensive in breakdown of ingredients in detergents. One thing she did bring up during our talk, and that she mentions here, is that some people think that SLS might be a carcinogen. She says she can’t find any evidence of this and neither can we. Maia links to the Snopes.com page about it, which talks about the possible origins of this rumor. The Environmental Working Group also classifies SLS as a low overall hazard and not a cancer risk.

In 2008 and 2009, the Organic Consumers Association tested a bunch of different shampoos, body washes, and dish detergents for 1,4-dioxane.10The products they tested were by no means extensive, but they did look at several different dish detergents.11 Many “green” dish detergents tested had levels of 1,4-dioxane around 100 ppm or so, but the manufacturers got these down to non-detectable amounts (below 0.2 ppm) when they were retested a year later. For the dish detergents they tested that had a detectable amount of 1,4-dioxane, the average amount was just below 3 ppm, and that number is skewed high by the 8.6 ppm reading of the Palmolive Pure & Clear Sparkling Fresh. Everything else was below 3 ppm, well below the popular limit.12

But for most of those detergents, the amount of 1,4-dioxane is very small, smaller than the limits for 1,4-dioxane in food, etc. Remember how much dish detergent you use when you’re doing dishes? About a teaspoon in a sink full of water. I decided to find out if this amount of 1,4-dioxane when washing dishes is enough to register any concern.

I have a pretty standard size sink in my house. I filled one side up with the amount of hot water I’d typically use to do a load of dishes, and it came out to about 2.6 gallons, or 10 liters (L). It took one teaspoon, or 5 milliliters (mL), of Target’s generic brand to produce about three inches of foam on top, about how much I’d use if I were doing a load of dishes. I want to get the amount of detergent in water into ppm so I can directly compare it to the limits the government agencies put on it, so I’ll need the weight per volume of the detergent. Different brands vary a tiny bit, but it’s about 1 gram (g) per mL, the same as water.13

first-formula

Since ppm is mg/L, we can say that this concentration of detergent in water is 500 ppm. Because I don’t know the concentration of 1,4-dioxane in this detergent, I’m going to use a high estimate of 10 ppm, based on the findings by the OCA. For simplicity’s sake, I’m going to write out ppm as a fraction. That’s 10 molecules of 1,4-dioxane in every 1 million molecules of detergent, which looks like this:

second-formula-top

Second-formula-bottom

 

The last number on the bottom is a billion. That makes 5 parts per billion of 1,4-dioxane in a sinkful of water. Not much.14 You would need to do about 2,000 sinkfuls of dishes and absorb all of it into your skin to get to the 10 ppm level. However, if you’re still concerned about it, avoid dish detergents with any ingredients containing the –eth suffix, plus PEG, which stands for polyethylene glycol. Also, you could don a pair of those yellow rubber gloves to do your dishes. As a bonus, you would avoid dishpan hands. Win.

Other ingredients of concern

Numero uno are phthalates—a class of chemicals known as plasticizers, which make hard plastics more flexible and therefore harder to break. Phthalates are found in hundreds of different products. You may have heard about them because there’s been some recent press about getting phthalates phased out of use in children’s toys. How exactly they affect human health, if at all, is not clear. They have caused harm to the reproductive systems of lab animals, but there haven’t been many human studies. CDC researchers have found phthalates (or metabolites) in many people they tested, leading them to say that exposure is “widespread.” The FDA says that they don’t pose a safety risk the way they’re used in cosmetics right now, but they’re keeping an eye on it.

In dish detergent, phthalates tend to be used in the fragrance mixture. But you won’t see anything that looks like a phthalate on the outside of a dish detergent bottle—per FDA rules, companies are not required to list the ingredients of a fragrance. However, choosing “fragrance-free” dish detergent will probably help you steer clear of this one. And many detergents, such as Seventh Generation, tend both not to use phthalates and to advertise that on the label.

Another compound to look out for is triclosan. It’s used as an antibacterial agent in many products, including dish detergent. And because it’s also used as a pesticide, this one is required to be on the label. As mentioned above, the FDA says antibacterial soaps with triclosan do NOT work better than regular soap. There isn’t any evidence that they kill more germs than regular old soap, and some studies say that the use of this compound is leading to more resistant bacteria. You’ve probably heard of these superbugs, and they have the potential to make us really, really sick.15 In fact, the FDA recently gave companies that make antibacterial soap a year to prove that it’s beneficial. As of January 2016, the FDA still hasn’t updated their page about triclosan. However, this study came out mid-September that found “Antibacterial soap containing triclosan (0.3 percent) was no more effective than plain soap at reducing bacterial contamination when used under ‘real-life’ conditions.”  So our stance was and still is to skip the triclosan.

The last on the list of the concerning chemicals trifecta are phosphates. Phosphates are pretty common—they make up the backbone of our DNA, for example—but too much of them can spell trouble for water systems, namely by algal bloom. Basically, algae in the water snaps up this yummy yummy food and reproduces like crazy, choking out other plants, fish, and aquatic wildlife. It used to be a problem, but in August 2010, 17 states passed a ban on high amounts of phosphates in lawn fertilizers and dish detergent (which includes handwashing dish liquid). Because of the nightmarish logistics that would go along with having phosphate containing detergent in some states but not others, companies just cut back on the amount of phosphate in all their products. More recently, Procter & Gamble, who makes Dawn and Tide, said that they’re going to cut back on phosphates in their products worldwide, phasing them out completely over the next two years. As such,  it’s unlikely that your dish detergent contains phosphates. To be sure, check the label.

How soap works

Why do we need to use soap on our dishes at all? Because oil and water don’t mix. Water molecules are made up of an oxygen atom with two hydrogen atoms on either side (H₂0). The elements stick together because they share little electrical charges—electrons. Oxygen’s a bigger electron hog than hydrogen, and pulls the electrical charge towards it, away from the hydrogens. Because of this unequal electron sharing, the water molecule has one part with a slightly negative charge (the oxygen) and another charged slightly positive (the hydrogens).

Oil, on the other hand, is mostly made up of carbon and hydrogen atoms. These are much better at sharing their electrons evenly, and as a result don’t have an overall electrical charge.

When you get oil and water together, both liquids bead up and try to minimize their contact with each other. The charged bits repel the non-charged bits, and vice-versa. Both liquids kind of fold up into themselves to try to minimize contact with one another. It is for this reason that you can rinse a plate gunked up with grease all day long, and while some might sloosh off just from the blast of water, to get it really clean you need a way to make the two different molecules mix. That’s soap.

Soap is pretty dang nifty. It’s made up of two opposite parts: one part that’s neutral so it can mix with oil, and one part that’s charged so it can mix with water. It looks like this:

06-diagram-one-dish-soaps-630

When soap molecules encounter a blob of grease in water, the neutral parts interact with the oil, while the charged parts interact with the water. It ends up forming a structure called a micelle16, which is kind of a spherical17 blob. It looks like this:

07-diagram-2-dish-soaps-630

The heads of the soap molecules point out, towards the water. And the tails point inward, towards the soap. By pulling the grease and water together, the soap allows water to dissolve the grease, which allows us to rinse it away. Victory!

All this said, dish detergent isn’t technically soap. What we call soap chemists call sodium stearate. The trouble is, sodium stearate actually isn’t that great at cleaning. It often reacts with the dissolved minerals in tap water to form a white solid. It’s this solid that sticks to the walls of your shower and the sides of your wine glass and is otherwise known as soap scum. When a molecule of soap forms a molecule of soap scum, that’s one fewer molecule that can form the micelles around grease, so it not only mucks up dishware and tiles, but it does not clean as well.

To get around the soap scum problem, scientists developed other soap-like molecules that don’t form scum as readily, because they don’t react as well with the types of minerals typically found in water. These are surfactants, short for surface active agent.

Surfactants are in all types of cleaning products from toothpaste to shampoos to dish detergents. And a detergent is a cleaning solution that contains one or more surfactants. According to surfactant expert Brian Grady, detergent companies put a combination of surfactants into detergents for foaming, cleaning, and not producing soap scum. They also put the smallest amount of surfactant in the bottle possible—they’re trying to make the detergent clean well, but also be cheap. Also, soaps and detergents tend to be irritants—all surfactants are designed to make oil rinse away in water, which includes the oils in your skin, so they can make your skin dry and itchy. Some soaps and detergents also are alkaline, so they might produce a burning sensation if you’re sensitive.18

By the way, dish soap works on seemingly low-grease foods. For example, even a vegetable like a dry-roasted pepper contains a ton of natural oils. And burnt on sugar is not all that molecularly different than oil—it’s mainly hydrocarbons, which are dissolved by the hydrophilic part of soap.

Detergents for babies

Perusing liquid dish detergents on Amazon brings up a few dish detergents that are marketed specially towards baby items, such as bottles, breast pump parts, and toys. But are these really any different from regular dish liquids? The three most prevalent baby targeted brands are Palmolive, Seventh Generation, and Dapple. Palmolive Baby has fewer ingredients than the original Palmolive dish liquid, and uses a different main surfactant.19 The baby variety also has three surfactants instead of two and a pH control agent instead of stabilizers to help keep it fresh. The only problem with the Palmolive Baby dish liquid is that many people complain about the residual fragrance (according to reviews on Amazon, Soap.com, and drugstore.com). Palmolive doesn’t make a fragrance-free baby dish liquid at the time of this writing.

Seventh Generation uses the exact same ingredients in its baby dish liquid as the original, just in slightly different concentrations. According to Brandi Thomas, their media relations person, the company increased the amount of some of the cleaning agents “to get at really tough, biological oils,” presumably such as fatty breast milk. Of course, much food residue is made up of biological oil. She also said that some of their employees use the baby dish liquid for really greasy pans. I then asked the obvious question, which is if this works so well on grease, why don’t they just make this formula the regular dish liquid? Thomas said that the company didn’t really think that people need this stronger formula for everyday use, since it is more expensive, but it is good for use on bottle and breast pump parts. And yes, it is more costly: Seventh Generation baby is almost twice as expensive per ounce as the regular Seventh Generation, $0.21 versus $0.11 on Amazon at the original time of writing this guide.

Dapple, which only makes baby-marketed products, also has a dish liquid. Dapple baby comes in a fragrance-free variety, and does not contain any SLS or SLES, instead using lauryl glucoside20 as a cleaning agent. The bottle promotes “baby-safe ingredients” and has a sticker on the bottle that claims “0 percent toxins.” This seems to imply that other dishwashing detergents are not baby-safe, and that Dapple is harmless, neither of which are true. Using the word “toxins” is also a bit strange, since the definition of a toxin is a biologically produced poison—think snake venom or the compound that causes botulism. When I pointed this out to the company, their representative, Kelsey O’Connor, told me that they mean that the detergent has the following attributes: It contains no SLS, no SLES, no parabens, no 1-4,dioxane, no dyes, no artificial fragrances, no phthalates, and the bottles are BPA-free. I again pointed out that none of these things are toxins, and while saying the detergent has 0 percent toxins is technically true21 this might mislead customers to think that the ingredients are harmless, which is not true, and surely they don’t mean to mislead their customers? This was Dapple’s official response:

“The claim ‘no toxins’ is completely true and forthright—not a single ingredient in our products is a toxin, and we disclose all ingredients to make sure everyone knows exactly what’s in there. The fact that something does not contain toxins, however, does not necessarily mean it is edible. As a result, we also clearly mark all products with a safety warning to that end.”

So there you go, folks. Dapple is your source for officially botulism-free dish liquid.

Deadly nerve toxins aside, do you really need a separate dish liquid for washing baby bottles and breast pump parts? We decided to do our own tests to find out. We followed the same protocol for the regular detergents: put a thin layer of oil on a plate, then submerge it in 10 liters of 70°F water with 5 mL of detergent mixed in, and beat it with an egg beater for two minutes. Then we compared the baby detergents to water, the regular Seventh Generation, and Dawn. And guess what? Both Palmolive Baby and Dapple removed more oil than the regular Seventh Generation and Dawn. Dapple was the best, leaving only about 5 percent of the oil on the plate. Palmolive Baby left behind about 10 percent of the oil. Seventh Generation Baby did not do as well and left about 25 percent of the oil on the plate, a worse performance than the regular Seventh Generation dish liquid.

But are these detergents worth it? Reviews from multiple sources sing the praises of these dish liquids, but they are more expensive. Dapple rings up at about $0.26 per ounce (although through that source you do have to pay shipping). The price of the Palmolive Baby seems to be all over the place online, but I got a 10-ounce bottle for $2.50 at my local Wal-Mart. At that price, it might be worth it to keep some for bottles and breast pump parts. But we would try out regular detergents first. If they don’t work for you, then maybe it’s time to bring in the big guns.

Footnotes:

1. The control was plates that had received the same treatment but with plain water instead of a water/detergent mixture. Jump back.

2. For those wondering why this one didn’t do as well as the original Dawn Ultra, it does have a slightly different formula. Jump back.

3. Some surfactants foam more than others. But how much they foam has nothing to do with how well they clean. And likewise, the absence of foam does not mean that your detergent is not cleaning. Jump back.

4. We only did it this way in testing to maximize the difference between the plain water and the detergents. Ditto for the 70°F water. This let us judge the detergents better because it was easier to tell the difference between them. Jump back.

5. We don’t recommend this. Jump back.

6. According to the American Burn Association, sticking your hand in 155°F water will cause a third-degree burn in 1 second. Jump back.

7. According to Grady, the oil industry makes more money each year from selling cleaning agent materials than they do from gas. Jump back.

8. They don’t make their own cleaning agents, they buy them, but she wouldn’t tell me from where. Jump back.

9. Remember, how foamy or bubbly a detergent is has nothing to do with how well it cleans. Grady said that some surfactants are just better at foaming than others. Jump back.

10. Unfortunately, the link to the actual test results still appears to be broken, despite my informing two separate people at the OCA of this. It took multiple and emails for them to send me a copy, but we can pass them along to anyone interested. Jump back.

11.Dawn was not among them, but Ellen Losey, their PR person, told us, “all Procter & Gamble household cleaning product will be at or below 25 ppm by the end of 2013. Many are already below 10 ppm.” However, she said that the company did not want to disclose the exact amount in their dish liquid. You can re-read the same basic statement here. Jump back.

12. The only exception to this is Mrs. Meyer’s Clean Day Liquid Dish Soap, which came in at 204 ppm of 1,4-dioxane. However, I talked to Pam Helms, the Chief Innovation Officer at Mrs. Meyer’s Clean Day. She says that they’ve reformulated their dish liquid since then, and their internal tests show no detectable level of 1,4-dioxane. Jump back.

13. Generally, the density of dish liquid is slightly higher. You can layer water on top of dish liquid, and it will drop to the bottom of a sink filled with water. We’re using 1 g/mL here as an approximation. Jump back.

14. I discounted the amount of 1,4-dioxane that might be found in my tap water, just because a) I don’t know how much it is, b) it might not be any at all since having a limit of something in water does not necessarily mean that there is any of it in your water, and c) it’s going to be different for everybody on based where you live and water quality. Jump back.

15. For a peek at what antibiotic resistant bacteria might lead to, please read Maryn McKenna’s article on the post-antibiotic future. Guaranteed to cause nightmares. Jump back.

16. This is the same basic structure that the cells in our bodies have as well, except our cell membrane are made up of phospholipids instead. Jump back.

17. A sphere is the most structurally stable type of shape, which is why it’s found so often in nature. Just ask a soap bubble. Jump back.

18. Soap is traditionally made with sodium hydroxide, aka lye, which is very very alkaline. If you’ve seen or read Fight Club, you know what this can do to your skin. If you spill some on yourself (I have), it actually makes your skin slimy. That’s your fat dissolving. Yum. Jump back.

19. Good old sodium laureth sulfate instead of ammonium pareth sulfate. According to Brian Grady, the surfactant expert, these are pretty much the same and clean about as well as each other. Jump back.

20. Also known as decyl glucoside. It’s made from glucose and an alcohol. Not a lot is known about this surfactant, but it’s supposed to be mild on skin. Jump back.

21. And therefore complies with the Fair Packaging and Labeling Act. Jump back.

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Originally published: January 26, 2016

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