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These Are the Chemicals That Should Not Be in Your Hair Products

Is 'sulfate-free' a good thing? What's up with parabens? What are the ingredients we should be avoiding completely?
WAA / Stocksy

Perusing the shampoo aisle at Target, you might notice that every other hair product is labeled “free” of some supposedly harmful ingredient—“paraben-free,” “silicone-free,” “sulfate-free.” That’s especially true for gentle products designed for the curly, textured hair that many people of color have, which tends to be drier and more prone to breakage than straight hair.

But given that most of us don’t read the entire inscrutable list of ingredients in our hair products, these labels raise more questions than answers. What are sulfates, and why are they bad? And are they actually bad, or is “sulfate-free” just a marketing phrase?


We spoke to Scott Masten, director of the National Toxicology Program’s office of nomination and selection, to come up with a quick run-through of common hair-product ingredients, what they do, and what we know so far about their harmful effects, if any. (It’s important to note, unfortunately, that not all the chemicals in a product even appear on the ingredients list. In a recent Environmental Research study of 18 hair products, 84 percent of the chemicals detected in the products weren’t listed on the label. How often products contain unlabeled ingredients remains unknown, Masten says, but it’s “an area of research interest.”)

It’s worth pointing out that the level of concern about these ingredients differs depending on who you ask. For instance, a consumer watchdog group might caution against the use of products containing these ingredients more aggressively than, say, a regulatory agency. And even regulatory agencies differ in their level of concern. Compared to regulators in the United States, those in the European Union tend to be more prudent about consumers’ chemical exposure. The US Food and Drug Administration has banned or restricted the use of 11 ingredients from cosmetics, while the EU has banned more than 1,000.

Indeed, a number of the ingredients listed below are banned or restricted in the EU. Bis (2-ethylhexyl) phthalate (DEHP) is banned, along with petrolatum, “except if the full refining history is known and it can be shown that the substance from which it is produced is not a carcinogen,” the EU Cosmetics Regulation states. The EU has also placed restrictions on parabens, as well as formaldehyde and formaldehyde-releasing chemicals, allowing them in only certain products or limiting their concentrations, for instance.


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To state the obvious, whether or not you buy products with the ingredients mentioned below comes down to personal choice and how comfortable you are with the potential risks outlined. For instance, while the connections between parabens and breast cancer risk aren’t clear yet, you can choose to avoid products that contain parabens if you’re particularly concerned about them (say, perhaps due to a history of the disease in your family). “There’s really no substitute for an active and thoughtful consumer to be seeking out that information and making informed decisions,” Masten says. (Given that not all compounds will even be listed on a label, the most concerned consumer could choose to cut back on all products, as one researcher recommended in a related Tonic story.)

Here is a list of common ingredients with the basics of what we know about each one.

Cetyl, oleyl, and stearyl alcohols: These fatty alcohols give shampoo and conditioner their thick, creamy consistency. They also have softening properties, making your hair feel smooth and supple. Masten says they have generally low toxicity, which is good because they’re pretty hard to avoid.

Diethanolamine (DEA): DEA acts as a thickening agent in shampoos and conditioners, and allows them to form a foamy lather. While the California Office of Environmental Health Hazard Assessment (OEHHA) added cocamide DEA to its list of chemicals known to be linked to cancer in 2012, the FDA states that “at the present time there is no reason for consumers to be alarmed based on the use of these substances in cosmetics.” Based on rodent studies, we know that cocamide DEA can cause cancer under certain conditions, Masten says. But the rodents “were administered DEA essentially for the majority of their lifetime at a level of exposure that is considerably higher than a consumer would experience from using a DEA-containing cosmetic product.”


Formaldehyde and formaldehyde-releasing chemicals, such as: 5-bromo-5-nitro-1,3-dioxane, DMDM hydantoin, imidazolidinyl urea, methylene glycol, oxomethane, and quaternium-15: Shampoos may contain preservatives that release formaldehyde, which Masten says is “not something you really want in any appreciable level.” He adds that “the primary health concern is skin reaction, skin sensitization,” or an allergic reaction to something after it comes into contact with skin. What’s more, “while some preservatives may have been tested and found to have low skin-sensitization potential, there is no requirement to do so.”

Similarly, hair smoothing treatments may contain methylene glycol or other ingredients that release formaldehyde gas when heated . The FDA cautions that formaldehyde in hair smoothing products has been associated with a number of reactions, such as rash, eye problems, headaches, dizziness, and vomiting. Ask your stylist if he or she knows whether a product contains ingredients that release formaldehyde or other ingredients you may want to avoid—or, even better, look it up ahead of time. “Know before you go’ may be a better approach,” Masten says. “Easier to do your homework in advance rather than wait until you are in a store or business.”

Fragrance: You’d be hard-pressed not to spot the word “fragrance” printed on a hair product label. “Fragrance” can include a mixture of ingredients that makes your conditioner smell like coconut or the Meatpacking District on a Saturday night, but regardless, the FDA doesn’t require companies to specify them, since this information is often proprietary and therefore outside government purview. If you have an allergic reaction to a product, fragrances are probably responsible. Researchers have also begun exploring their links to asthma. “In general, there’s enough evidence that some fragrance ingredients can exacerbate asthma in some individuals,” Masten says. But “we don’t’ necessarily know which individuals would be affected or which fragrance ingredients are the culprit.” If you’re worried, shop for products labeled “fragrance-free.”


Mineral oil: Mineral oil, also listed as paraffin oil or white mineral oil, forms a protective coating over hair that locks in moisture. Some worry that it could cause cancer since it’s distilled from petroleum, produced during the refining of crude oil—and mildly or untreated mineral oil is known to be a carcinogen. But highly refined, cosmetic-grade mineral oil and other cosmetic-grade petroleum distillates, like petrolatum (see below), are “generally of low concern,” Masten says.

Petrolatum: Like mineral oil, petrolatum—also listed as white petrolatum and petroleum jelly—is a petroleum distillate, but has a more viscous consistency. Widely used as a topical ointment, it forms a protective coating that traps moisture, and adds body and shine. “It would be of low toxicity concern,” Masten says.

Parabens: Parabens such as methylparaben and propylparaben prolong the shelf life of hair and other beauty products by preventing bacteria and mold growth. Some evidence suggests they may contribute to breast cancer development, but “most of what we know from parabens come from either animal studies or in vitro studies—cell cultures in the lab,” Masten says. For now, it’s not entirely clear how parabens affect breast cancer risk in humans. “There will be some time before we have information that is conclusive on whether they cause any particular adverse health effects.” Until then, if you’re concerned, choose products labeled “paraben-free.”


Pthalates: Diethyl phthalate (DEP), the only phthalate still widely used in beauty products, acts as a solvent for fragrances. According to the FDA website, “based on available safety information, DEP does not pose known risks for human health as it is currently used in cosmetics and fragrances.” But if you still prefer to steer clear of products containing DEP, shop for those whose list of ingredients doesn’t include fragrances.

Studies have linked the less commonly used bis(2-ethylhexyl) phthalate (DEHP), which can be found in hair relaxers, to male reproductive development problems. “There’s enough adverse health effects known or suspected with DEHP to be concerned,” Masten says, although “its use in certain products has declined.”

Propylene glycol: Propylene glycol is an alcohol that helps hair absorb and trap moisture, and can function as a solvent for other ingredients. Compared to other common ingredients, there’s “not a lot of concern about toxicity or hazard” for propylene glycol, Masten says.

Silk protein: A protein spun by the silkworm, silk acts as a conditioning agent and adds bulk to products. The Cosmetic Ingredient Review has concluded that eight silk proteins—fibroin, hydrolyzed fibroin, sericin, hydrolyzed sericin, silk, hydrolyzed silk, silk extract and silk powder—are safe as used in beauty products. But overall, Masten describes the extent of available safety information for the silk protein products used in cosmetics as “considerably less than for other common ingredients.” Given that, he says, he doesn’t feel he can make a recommendation about it one way or the other.

Sulfates: Often in the form of sodium laureth sulfate and sodium lauryl sulfate, sulfates give shampoo its sudsy-ness, and cut through grease and dirt. But they can also strip away natural oils in the process, which can lead to frizzy, dried-out strands, and an irritated scalp. “There are not any large hazard concerns with them, but the trend seems to be to find less harsh ingredients,” Masten says.

Silicones: Silicones—whose names often end in –methicone or –oxane—form a waterproof coating over hair that keeps it from soaking up humidity, making them common in straightening and smoothing products. The coating also seals moisture inside the hair, and makes it shiny and easier to comb. But some silicones, like dimethicone, can also cause heavy buildup that leaves strands limp and dull. A class of silicones known as cyclosiloxanes is gaining growing attention from the research community, who has begun investigating concerns about whether they can cause cancer or disrupt the endocrine system. But that research is still “sort of early,” Masten says.

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