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Do you really know how many toxic ingredients do you spread over your hair everyday? There are hundreds of different chemicals in hair products available in stores and online. They have different hair growth / anti-hair-loss properties, and… surprise! They also come with a different mix of (really, really bad) chemicals.

Worst Chemicals in Hair Products

Since beauty hair products are applied directly not only on the scalp, but onto the whole body (i.e. under the shower), it’s inevitable that particles are continuously, day by day, absorbed by our skin. On the long run, these chemicals in hair products accumulate in your system, leading to harmful side effects.

Each of the chemicals listed below has a growing list of evidence that show long-term health issues like cancer, hormonal dysfunctions and other different possible diseases. Although we focus on hair products only in this article, it’s worth mentioning all the chemicals listed are also present in other personal care and household products.


1,4-dioxane chemical structure
1,4-dioxane can be found in 20 percent of cosmetics products, yet, it is absent from ingredient lists! That’s because 1,4-dioxane is a contaminant produced when ingredients mixed together react to form a compound. But when applied with certain preparations such as lotions, 1,4-dioxane penetrates the skin easily. Exposure to high quantities, 1,4-dioxane is a probable carcinogen and is linked to severe kidney and liver effects, and sometimes death.

  • Products: hair relaxers. shampoos
  • On the Ingredient List: “PEG compounds”, “xynol”, “sodium laureth sulfate”, “ceteareth or “oleth”
  • Possible Health Problems: from eye and nose irritation to possibly cancer and organ toxicity
  • At-Risk Populations: infants, teenagers, pregnant women and animals

Butylated Compounds

Butylated hydroxytoluene (BHT) chemical structure
Butylated hydroxyanisole (BHA) and butylated hydroxytoluene (BHT) are derivative of phenol, prized for their antioxidant properties and used as preservatives in different hair care products. BHA and BHT are connected to cases of endocrine disruption, organ-system toxicity, and other health problems.

  • Products: various hair products
  • On the Ingredient List: “BHA” and “BHT”
  • Possible Health Problems: endocrine disruption, developmental and reproductive toxicity, organ-system toxicity, cancer
  • At-Risk Populations: infants and pregnant women

Coal Tar

Coal chemical structure
Coal tar is produced during the incomplete combustion of coal and is a well-known carcinogen. Made of hundreds of compounds (e.g. polycyclic aromatic hydrocarbons or PAHs), coal tar can produce tumors and neurological damage. According to FDA, Any hair care products must display a warning label if they contain coal tar at levels of 0.5% to 5%, and must indicate specific precautions for that product.

  • Products: Shampoos and scalp treatments, hair dyes
  • On the Ingredient List: “tar”, “coal tar solution”, “coal”, “crude coal tar”, “estar”, “lavatar”, “carbo-cort”, “impervotar”, “KC 261”, “picis carbonis”, “high solvent naphtha”, “naphtha distillate”, “naphtha”, “benzin B70”, or “petroleum benzin”
  • Possible Health Problems: cancer and organ system toxicity
  • At-Risk Populations: all

Ethanolamine Compounds (MEA, DEA, TEA)

Diethanolamine chemical structure
Ethanolamines are present in many hair products such as shampoos, hair conditioners and dyes, and is connected to liver tumors. In Europe, diethanolamine (DEA) is prohibited in cosmetics by the European Commission.

  • Products: Shampoos, hair conditioners and hair dyes
  • On the Ingredient List: “diethanolamine”, “DEA”, “triethanolamine” “TEA”, “DEA-cetyl phosphate”, “DEA oleth-3 phosphate”, “oleamide DEA”, “lauramide DEA”, “linoleamide MEA”, “myristamide DEA”, “TEA-lauryl sulfate”, “stearamide MEA, “cocamide DEA” or “cocamide MEA”
  • Possible Health Problems: cancer and organ system toxicity
  • At-Risk Populations: all


Formaldehyde chemical structure
Formaldehyde and formaldehyde-releasing preservatives (FRPs) are particularly used  in shampoos. Used to help preventing microbes from developing in water-based products. formaldehyde can be easily absorbed through the skin and is linked to allergic skin reactions and even cancer.

  • Products: shampoos, baby shampoos and hair-smoothing products
  • On the Ingredient List: “formaldehyde”,  “polyoxymethylene urea”, “DMDM hydantoin”, “imidazolidinyl urea”, “diazolidinyl urea”, “glyoxal”, “sodium hydroxymethylglycinate” or “2-bromo-2-nitropropane-1,3-diol”.
  • Possible Health Problems: cancer and skin irritation
  • At-Risk Populations: infants and hair salon workers

Methylisothiazolinone and Methylchloroisothiazolinone

Methylisothiazolinone chemical structure
Methylisothiazolinone (MIT) and Methylchloroisothiazolinone (CMIT) are preservatives that can be found in many hair products, and are linked to possible neurotoxicity, allergic reactions and lung toxicity.

  • Products: shampoo, baby shampoo, hair conditioner, hair spray and hair color
  • On the Ingredient List: “OriStar MIT”, “Microcare MT”, “MI”,  “MCI”, “2-methyl-4-isothiazoline-3-one”, “5-Chloro-2-methyl-4-isothiazolin-3-one” or “Neolone 950 preservative”
  • Possible Health Problems: neuro-toxicity, allergies and inhalation toxicity
  • At-Risk Populations: individuals who are allergic to Methylisothiazolinone (MIT) or Methylchloroisothiazolinone (CMIT)


Octyl-methoxycinnamate chemical structure
Octinoxate (or Octyl methoxycinnamate – OMC), is used as a UV filter to protect the products from degrading when exposed to the sun. Knowing that octinoxate is an endocrine disruptor that mimics estrogen and can disrupt thyroid function, and is absorbed rapidly through the skin, you understand that . Unfortunately, octinoxate is approved for use in cosmetics throughout the world, the maximum authorized concentration depending on local legislation.

  • Products: shampoos and hair color
  • On the Ingredient List: “octinoxate”, “o methoxycinnamate (OMC)”, “escalol”, “2-ethylhexyl p-methoxycinnamate”, “parsol”, “parsol MCX”, or “parsol MOX”
  • Possible Health Problems: organ system toxicity, endocrine disruption, reproductive and developmental toxicity
  • At-Risk Populations: all


Paraben chemical structure
Parabens are preservatives used in a wide variety of personal care products and foods to prevent microbes from growing. These endocrine-disrupting chemicals may be absorbed not only through blood, but also by the digestive system and even through skin. Parabens have been found in breast cancer tissue and may play a role in breast cancer development.

  • Products: shampoos and hair conditioners
  • On the Ingredient List: “butylparaben”, “ethylparaben”, “isobutylparaben”, “isopropylparaben”, “methylparaben”, or “propylparaben”
  • Possible Health Problems: reproductive toxicity, cancer and endocrine disruption
  • At-Risk Populations: young children and pregnant women


Phenoxyethanol chemical structure
Phenoxyethanol is used as a preservative in hair products to limit bacterial growth. Reactions ranging from eczema to life-threatening allergic reactions are linked to phenoxyethanol. Also, infant oral exposure to phenoxyethanol can severely impact on certain nervous system functions.

  • Products: shampoos, hair conditioners, hair spray and hair color
  • On the Ingredient List: “phenoxyethanol”, “2-Phenoxyethanol”, “PhE” or “Euxyl K® 400”
  • Possible Health Problems: allergies and nervous system effects (infants)
  • At-Risk Populations: individuals allergic to phenoxyethanol and breast-feeding infants.


Quaternium-15 chemical structure
Quaternium-15, a known skin toxicant and allergen, may be especially dangerous when in contact for long periods of time. In the US, there are still no regulations for quaternium-15 use in hair products.

  • Products: Hair conditioners and hair styling products
  • On the Ingredient List: “Quaternium-15”, “benzalkonium chloride”, “benzethonium chloride”, “centrimonium bromide”, or “polyquaternium–n” (“n” being a number – i.e. “polyquaternium–3”).
  • Possible Health Problems: Irritation and sensitization
  • At-Risk Populations: all, but especially dangerous for hairdressers and janitors

Check Your Cosmetics’ Ingredients

If you are wondering about an ingredient’s toxicity in your everyday hair care product, make sure to use this Ingredient Checker tool 😉 Just type an ingredient, a product or a brand name in the search box and you’ll know everything about it!

Even if well-documented and carefully written, this content should not be used as a substitute for professional diagnosis and treatment. Consult a qualified health care provider before making any health care decisions about any specific medical condition.

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Vincent P.

Vegan entrepreneur, humanist, animal's rights defender