Ethanolamines (DEA, TEA, MEA) in Cosmetics: The Nitrosamine Risk, and Why the US Still Allows What Canada and the EU Don’t

Georden Jones, Founder, The Peer Review · Last updated: August 29, 2026

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The Short Answer

Diethanolamine, triethanolamine, and monoethanolamine, known by their initials DEA, TEA, and MEA, are a family of related chemicals used to adjust pH and build foam in shampoo, soap, and liquid cosmetics. The hazard behind this ingredient family is not the ethanolamines themselves in isolation. It is what they can turn into. When DEA or TEA sits in the same formula as a nitrosating agent, a category that includes some common preservatives like bronopol, it can react to form N-nitrosodiethanolamine, a compound the US National Toxicology Program found caused liver and kidney cancer in mice after repeated skin application in a two-year study [1][2]. Cocamide DEA, a related foam booster made by reacting DEA with coconut oil, has been on California’s Proposition 65 carcinogen list since 2012 for the same reason, and as recently as 2023 and again in a 2026 enforcement notice, watchdog testing and state legal filings have found it in shampoos and body soaps sold at major retailers [3][4]. Canada has gone further than California’s warning-label approach: Health Canada classifies DEA itself as unacceptable for use in cosmetics outright, while the European Union prohibits it entirely under its own cosmetics regulation [5][6]. The US federal government, by contrast, has never banned DEA. Since 1979 the FDA has simply recommended manufacturers keep DEA concentrations under 5% in products meant for direct, prolonged skin contact, a guideline with no legal force behind it [1].

Evidence Rating: Mixed Signals. DEA and cocamide DEA causing cancer in animal studies through repeated skin application is General Consensus, based on the National Toxicology Program’s own two-year carcinogenesis study, though the agency itself has noted this has not been confirmed as a direct human cancer risk from typical cosmetic use [1][2]. The contamination mechanism, DEA or TEA reacting with nitrosating preservatives to form carcinogenic nitrosamines, is Strong Consensus and is the specific mechanism both Health Canada and the EU regulate against directly [5][6]. Whether ordinary consumer exposure to properly formulated, nitrosamine-free ethanolamine products causes human cancer is Not Enough to Say, since the animal data used dermal application at levels and durations that do not map cleanly onto typical shampoo or soap use. The regulatory gap here is unusually wide: two of the three regulators most relevant to Canadian readers have banned the riskiest version of this ingredient outright, while the third has only ever issued a voluntary concentration recommendation.

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Table of Contents

• Identify: What Ethanolamines Are, and Why DEA Is the One to Watch
• Where It Hides
• How It Affects You and Enters the Body
• Investigate: The Animal Cancer Data vs. the Contamination Mechanism
• What Canada Regulates, and What It Does Not
• What Canada, the US, and the EU Require
• Inform: What This Means for You
• Improve: How to Reduce Risk Without Overreacting
• What This Does Not Mean
• FAQ
• The Bottom Line
• References

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Identify: What Ethanolamines Are, and Why DEA Is the One to Watch

Ethanolamines are a small family of related chemicals built from ammonia and ethylene oxide, and cosmetic chemists use them for two main jobs: neutralizing acids to adjust a formula’s pH, and reacting with fatty acids to create foam-boosting, thickening surfactants like cocamide DEA and cocamide MEA [1][7]. Monoethanolamine has one reactive amine group, diethanolamine has two, and triethanolamine has three, a structural difference that turns out to matter directly for the risk profile of each one, since DEA’s two reactive amine sites make it the most efficient of the three at forming nitrosamines when a nitrosating agent is present [1][6].

The hazard is not the ethanolamine molecule sitting alone in a bottle. It is a reaction. Nitrosating agents, a category that includes some common preservatives, certain contaminants in raw materials, and even nitrogen oxides from air pollution, can react with DEA or TEA to form N-nitrosamines, a well-established class of carcinogens studied extensively in contexts ranging from cured meat to rubber manufacturing [6][7]. This is why regulators do not simply ask whether a product contains DEA. They ask whether the full formula also contains something that could react with it.

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Where It Hides

Ethanolamines and their fatty-acid derivatives, cocamide DEA and cocamide MEA especially, turn up across a wide range of everyday personal care and household products [1][3][7]:

• Shampoo and liquid soap. Cocamide DEA is added specifically as a foam booster and thickener, and it is the single most common source of DEA exposure for most people.
• Bubble bath and body wash. Same foam-boosting role as shampoo, often at similar concentrations.
• Liquid hand soap and dish soap. A common, less-discussed source, since these products get frequent, repeated hand contact throughout the day.
• Some cosmetics and lotions. TEA in particular is used as a pH adjuster in creams, lotions, and sunscreens, a leave-on use pattern that carries a lower EU concentration limit than rinse-off products because of longer skin contact time.
• Some hair-styling and permanent-wave products. MEA is used in some of these formulas, generally restricted to rinse-off applications where regulators allow it.

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How It Affects You and Enters the Body

The exposure pathway for this ingredient family runs almost entirely through the skin, which is also the exact pathway used in the animal studies regulators rely on [1][2][6]:

• Dermal absorption during use is the dominant route. Shampoo, soap, and lotion containing these ingredients sit on the skin and scalp during application and rinsing, and the National Toxicology Program’s own carcinogenicity findings came specifically from repeated dermal application in mice, not from ingestion or inhalation [1][2].
• The nitrosamine reaction can happen inside the product itself, before it ever touches you. If a formula contains both DEA or TEA and a nitrosating agent, the reaction can occur during manufacturing or storage, meaning the finished product on the shelf may already contain trace N-nitrosodiethanolamine by the time you buy it, independent of anything happening on your skin [6][7].
• Repeated, chronic contact matters more than a single exposure. The animal studies that found liver and kidney tumors used repeated dermal application over an extended period, which is why regulatory attention has focused on formulation-level nitrosamine prevention rather than on any single product use [1][2].
• Ingestion and inhalation are minor pathways for typical cosmetic use, relevant mainly in industrial or occupational settings where these chemicals are handled in concentrated, undiluted form rather than as a small percentage of a finished shampoo or soap.

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Investigate: The Animal Cancer Data vs. the Contamination Mechanism

1. The National Toxicology Program’s dermal carcinogenicity findings (strong animal evidence, unclear human relevance). In a two-year study, the NTP found that repeated skin application of DEA and cocamide DEA caused liver and kidney cancer in mice [1][2]. This is a real, government-run, peer-reviewed finding, not an activist claim, and it is the direct basis for cocamide DEA’s Proposition 65 listing in California [3]. What the NTP study did not do is establish a confirmed link to human cancer from typical cosmetic use, since translating a dermal mouse carcinogenicity study directly to human shampoo use involves real uncertainty around dose, duration, and species differences that toxicologists have not fully resolved [1].

2. The nitrosamine contamination mechanism (well-established chemistry, the actual regulatory target). This is the mechanism both Health Canada and the EU regulate against directly, and it does not depend on resolving the mouse-to-human cancer question at all. N-nitrosamines, the compound class formed when DEA or TEA reacts with a nitrosating agent, are well-studied carcinogens across multiple contexts outside cosmetics entirely, and the EU’s approach reflects this: rather than banning TEA outright, it caps allowable nitrosamine content in the finished product at 50 micrograms per kilogram and separately restricts the raw material’s secondary amine content, attacking the contamination pathway directly instead of relying on avoiding a single trigger ingredient [6][7]. DEA, with two reactive amine sites instead of TEA’s chemistry-buffered three, forms nitrosamines more readily, which is the specific reason the EU and Canada treat it more strictly than TEA or MEA [1][6].

3. Ongoing market presence despite the known risk (an enforcement and awareness gap, not a scientific one). The chemistry and the hazard have been documented since at least the late 1970s, when the FDA first issued its voluntary concentration guidance [1]. Yet a consumer watchdog group found cocamide DEA in shampoos and body soaps at major retailers as recently as 2023, and a 2026 California Attorney General enforcement filing shows Proposition 65 notices continuing to be issued over the same ingredient [3][4]. This is not a case where the underlying science is unsettled. It is a case where a known, regulable risk keeps reappearing in the US market because there is no federal ban behind the FDA’s decades-old voluntary recommendation.

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What Canada Regulates, and What It Does Not

Health Canada draws a clear line within this ingredient family rather than treating DEA, TEA, and MEA identically. DEA is classified as unacceptable for use in cosmetics in Canada, a stricter designation than a mere concentration limit [5]. TEA and MEA remain acceptable, but with real conditions attached: formulas must be designed to be non-irritating, MEA is restricted to rinse-off products only, and none of the three may be combined with nitrosating agents in the same formulation, since that combination is what actually produces the carcinogenic nitrosamine [5].

What Health Canada does not do is require pre-market testing of finished cosmetic formulas to confirm they are actually free of nitrosamine contamination before the product reaches shelves. Compliance is enforced primarily through the same post-market Cosmetic Notification Form and periodic verification sampling used across most other cosmetic ingredient categories in Canada, not through mandatory batch testing before sale [5].

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What Canada, the US, and the EU Require

Requirement	Canada	United States	European Union
DEA in cosmetics	Classified unacceptable; effectively banned [5]	No federal ban; FDA recommends keeping concentration under 5% in skin-contact products, a voluntary guideline [1]	Prohibited outright under Annex II [6]
TEA in cosmetics	Acceptable in non-irritating formulas, not combined with nitrosating agents [5]	No specific federal concentration limit	Capped at 2.5% in leave-on products, 5% in rinse-off products; nitrosamine content capped at 50 µg/kg [7]
MEA in cosmetics	Acceptable, rinse-off products only, non-irritating formulas [5]	No specific federal concentration limit	Restricted under the same nitrosamine-prevention framework as TEA
Cocamide DEA specifically	Subject to the same DEA restriction as the parent ingredient [5]	No federal restriction; listed as a carcinogen under California’s state-level Proposition 65, requiring a warning label on products sold in that state [3][4]	Subject to the DEA prohibition, since it is a DEA derivative [6]

The pattern here is unusually stark compared to most ingredients on this site: Canada and the EU have both independently reached the same conclusion, that DEA specifically should not be in cosmetics at all, while the US federal government has never gone beyond a voluntary concentration recommendation issued in 1979. The only US-level consumer protection with real teeth is California’s Proposition 65 warning requirement, a state law, not a national one, which is why cocamide DEA can still legally be sold in shampoo across most of the United States outside California.

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Inform: What This Means for You

• DEA is banned or effectively banned in both Canada and the EU, but not in the United States. The US relies on a voluntary 1979 concentration guideline with no enforcement mechanism behind it [1][5][6].
• The hazard is a chemical reaction, not the ethanolamine molecule alone. DEA and TEA only form the carcinogenic nitrosamine when combined with a nitrosating agent in the same formula, which is why regulators focus on formulation rules rather than banning every product that lists the ingredient [6][7].
• Cocamide DEA keeps showing up in US shampoos and soaps despite being a known, regulated carcinogen in California. Watchdog testing found it in products as recently as 2023, and enforcement notices were still being filed in 2026 [3][4].
• TEA and MEA are treated less strictly than DEA by every regulator that distinguishes between them, reflecting DEA’s greater chemical reactivity in forming nitrosamines [1][5][6].
• The strongest human cancer evidence available is still animal data from dermal application, not confirmed human epidemiology, which is a real limitation worth understanding even as it does not erase the reasons Canada and the EU have restricted the ingredient anyway [1][2].

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Improve: How to Reduce Risk Without Overreacting

1. Check ingredient lists for DEA, cocamide DEA, and lauramide DEA specifically, since these carry the strongest evidence and the clearest regulatory action from Canada and the EU [1][5][6].
2. TEA and MEA do not need the same level of concern as DEA, given that both Health Canada and the EU treat them as acceptable under proper formulation conditions rather than restricting them outright [5][7].
3. If a product is formulated and sold in Canada, it is already supposed to comply with Health Canada’s DEA restriction, which meaningfully lowers your exposure risk compared to products manufactured only to the looser US federal standard [5].
4. California’s Proposition 65 warning label is a useful signal even outside California, since a product carrying that warning for cocamide DEA is disclosing something the manufacturer may not flag on packaging sold elsewhere in the country [3][4].
5. Favor DEA-free foam boosters where you have a choice, such as cocamide MIPA or other alternative surfactants, particularly in products used frequently and left on the skin rather than rinsed off quickly.

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What This Does Not Mean

This is not a case for treating every foaming shampoo or soap as an active carcinogen sitting on a store shelf, and it is not a case for shrugging off a real chemical hazard that two major regulators have already acted on. The National Toxicology Program’s own dermal carcinogenicity findings in mice are a legitimate, government-conducted basis for concern, and they are exactly why Health Canada classifies DEA as unacceptable and the EU prohibits it outright, rather than the two regulators overreacting to speculative or activist-driven claims. At the same time, the human cancer risk from typical, occasional cosmetic use has not been confirmed the way the animal data has, and TEA and MEA, the two other members of this ingredient family, carry meaningfully less concern and remain permitted under conditions by every regulator examined here. The real gap worth your attention is not the underlying chemistry, which is well understood and consistently described across all three jurisdictions. It is that US federal law has never converted a forty-five-year-old voluntary recommendation into an enforceable rule, leaving cocamide DEA free to keep reappearing in American shampoos long after Canada and the EU closed the door on it.

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FAQ

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The Bottom Line

Ethanolamines are a small, related family of pH-adjusting and foam-boosting ingredients, and DEA is the one with the strongest evidence against it: a National Toxicology Program dermal study found it and its derivative cocamide DEA caused liver and kidney cancer in mice, and the chemical can react with certain preservatives to form a carcinogenic nitrosamine even without any additional exposure on your part [1][2]. Canada classifies DEA as unacceptable for cosmetics, and the EU prohibits it outright, while the United States has relied on nothing stronger than a voluntary 1979 concentration recommendation, a gap wide enough that cocamide DEA has kept turning up in US shampoos and soaps as recently as 2023, with California enforcement action continuing into 2026 [3][4][5][6]. TEA and MEA carry meaningfully less concern and remain permitted by every regulator examined here under proper formulation rules. If you want to close this specific gap, check ingredient lists for DEA, cocamide DEA, and lauramide DEA, and do not assume a US-market shampoo has automatically met the same bar Canada and the EU already require.

Stay curious, stay critical.
Georden

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References

1. US Food and Drug Administration. “Cosmetics: Diethanolamine.”
2. “Risk Assessment of N-Nitrosodiethylamine (NDEA) and N-Nitrosodiethanolamine (NDELA) in Cosmetics.” Journal of Toxicology and Environmental Health, Part A.
3. Center for Environmental Health. “CEH Takes Legal Action Against Amazon, Target, and Walmart for Selling Shampoos and Body Soaps Containing a Carcinogenic Chemical.”
4. California Office of the Attorney General. “Proposition 65 Notice, 2026.”
5. Health Canada. “Cosmetic Ingredient Hotlist: Prohibited and Restricted Ingredients.”
6. European Chemicals Agency. “Cosmetic Products Regulation, Annex II, Prohibited Substances.”
7. Safety Assessment of Triethanolamine and Triethanolamine-Containing Ingredients as Used in Cosmetics. International Journal of Toxicology, 2013.

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Georden Jones is the founder of The Peer Review. Read the full story.