What makes Hair Dye So Toxic?

Learn why hair dye might contain toxins that you would want to avoid if you are trying to live a clean beauty lifestyle. Think of this as Hair Dye 101.

We are Dyeing to Know

Did you know that as of 2019, over 64 million people used hair coloring products on their hair and 75% of American women dye their hair today? How crazy is that! With that number being so high, we are determined to get to the bottom of what the heck are in hair dye ingredients and why they could be toxic.

So think of this as your Hair Dye 101 class.

What is Permanent Hair Dye?

Permanent hair color is as the name suggests—permanent. When applied to your hair, it adds to your natural hair pigment so that the chosen color can replace it. Permanent hair dyes do this by opening the cuticle to let formula into the hair follicle to deposit the permanent color.

There is always a Developer, and Alkaline Agent, Colorants, and other ingredients. See below for the typical 4 step process. 


Here are some ingredients that prevent a permanent hair color from being called “non-toxic” or “safe:”

  • Hair Cuticle Opener
  • Hair Dye Colorants
  • Fragrance
  • Others: Surfactants, Emulsifiers, Preservatives, Silicones

Ammonia or ammonium hydroxide


Ammonia is used in hair color to open the cuticle and deposit the color.  This ingredient is not only toxic but can also be damaging to your hair and the environment. Ammonia can cause respiratory and asthma. (4).  Besides inhaling the toxic fumes either as a client or a stylist, once it is on a scalp it seeps into the pores, which is then carried into the bloodstream. 

So, if a permanent hair colorbrands calls their products “ammonia-free,” what ingredient does it use instead of ammonia?  Commonly, it is Ethanolamine that replaces ammonia in ammonia-free hair color brands.  However, ethanolamine is not at all safer than ammonia.



Ethanolamine is an ingredient used instead of ammonia to open hair cuticles and permanently cover grey hair. Though not as strong of a smell as Ammonia, ethanolamine has an ammonia-like odor.

This study found that hair colors with ethanolamine versus ammonia are more likely to cause hair loss. Although, Ethanolamine has not yet been evaluated for cancer risks, there is some evidence that it may elevate the risk of birth defects

Definition to know: Sensitizer

sensitizer is a chemical that may cause an allergic reaction in a person after several uses. The European Scientific Committee on Consumer Safety (SCCS) assessed hair dyes for skin sensitization potency.

Extreme: P-Phenylenediamine PPD

Strong: p-aminophenol, m-aminophenol, 4-amino-2-hydroxytoluene

Moderate: resorcinol, 2-methylresorcinol, 4-chlororesorcinol

Insufficient Testing: 2-amino-4-hydroxyethylaminoanisole sulfate

Arylamines P Phenylenediamine PPD


Arylamines – P-Phenylenediamine (PPD) functions as the main coloring agent in hair dye and it helps the color to last through shampoos. European Union Scientific Committee on Consumer Safety (SCCS) deems p-phenylenediamine (PPD) to be an extreme sensitizer.  

PPD is one of the most dangerous chemicals found in hair dyes. It has been known to cause bladder cancer and to cause cancer in animals in studies. 

PPD alone is toxic but when paired with Hydrogen peroxide it can become even more of an issue. Hydrogen peroxide is what’s used in formulations with the PPD to get it to activate. Many stylists can end up with skin irritation or dermatitis because of constant exposure to PPD and those getting their hair dyed report eczema and dermatitis. Studies link it as a possible carcinogen. (3)

P aminophenol, M Aminophenol, amino 2 hydroxytoluene


P-aminophenol, M-aminophenol, 4-amino-2-hydroxytoluene are all hair coloring agents in hair dye and a strong sensitizer. 



Resorcinol is a hair coloring agent in hair dye and a moderate sensitizer. One reasons for it’s toxicity, is because it may suppress thyroid function in case of dermal exposure to ulcerized skin at high doses (SCCS)and the European Chemicals Agency indicates hormone disruption assessment.

Toluene 2,5 diamine TDS


Toluene-2,5-diamine (TDS) Toluene is used in permanent hair dyes and is an extreme sensitizer. It is typically used instead of PPD.  Besides getting headaches, getting dizzy and having allergic reactions, long term exposure can lead to female reproductive system damage and pregnancy loss.  (6)

A sensitizer is a chemical that may cause an allergic reaction in a person after several uses.

Ethoxylated Ingredients


  • Polysorbate 20 Steareth-21
  • PEG-2 Soyamine
  • PEG-4 Rapeseedamide
  • PEG-7 Glyceryl Cocoate
  • Sodium Laureth Sulfate
  • Sodium Myreth Sulfate
  • PEG-3 Distearate
  • PEG-150 Distearate

are ethoxylated ingredients and may be contaminated with potentially carcinogenic 1,4-dioxane even though they do not list it as an ingredient unless explicitly tested.



Fragrance is usually a combination of numerous ingredients, some of which can be allergenic and endocrine disruptive especially those like Citronellol,  Geraniol, or Linalool if they are not derived from pure essential oils. Also, phthalates are likely to be present.  There are several different phthalates and some of them are possible carcinogens and hormone disruptors such as styrene.

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