93 (and counting) common shampoo ingredients they know cause contact dermatitis

Did you know formaldehyde (the stuff that preserves corpses) is commonly found in your shampoo?

Or you’re often scrubbing cat pee or raw alcohol on your scalp?


Well, you’ve come to the right place….

The vast majority of shampoos are bottles of chemical soup.

These chemicals will make the shampoo foam, smell nice, clean and last longer than a pint of milk.

They aren’t all bad.

Unfortunately, they aren’t all good either.

In a study on perfumes/cosmetics, it was found that 84% of the ingredients had never been tested or have minimal testing for human toxicity. Perhaps not surprisingly with such poor testing in place, these ingredients can cause all sorts of irritable or allergic reactions in people. The situation is exactly the same with shampoos.

The testing regime is extremely poor.

These irritant and allergic reactions you get from your cosmetics are called Contact Dermatitis and so few of us know we even have it.  It took me years and numerous dermatologist visits before I understood what was happening with my skin.

The growth in allergies has seen a big rise in free from foods but what about the skincare products you use? It is just as important to understand what you use on your skin when you have allergies, eczema, dermatitis or psoriasis…

Ruth Holroyd whatallergy.com

If you suffer reactions to shampoos and you’re not sure why, you’ve come to the right place. We’ve listed over 90 ingredients commonly found in our shampoos which the manufacturers know cause contact dermatitis.

The Sulfates

Sodium Lauryl Sulfate (SLS) is the harshest of the sulfates commonly found in shampoos. It’s both a foaming agent and cleanser found in many thousands of cosmetics. It’s so good at cleaning it is commonly used as an engine cleaner. As it’s so good at stripping oils, it strips the natural oils from your hair and skin and is one of the primary skin irritants found in many, many cosmetics today. There’s been quite a bit press about it and people are relatively aware of this additive. The manufacturers are wise to this, have seen the rise in sales of SLS free shampoos. so you’ll often see SLS labeled under different names. These include; called Sodium Dodecyl Sulfate, Sulfuric acid, Monododecyl Ester, Sodium Salt, Sodium Salt Sulfuric Acid and Monododecyl Ester Sodium Salt Sulfuric Acid.

There is a derivative of Sodium Laureth Sulfate (aka SLES/Sodium Lauryl Ether Sulphate among other things) which is a cheap alternative to SLS. It forms the same purpose as SLS, acting as a foaming agent and cleanser. Although it is generally considered milder than SLES, for sensitive skin sufferers it is still an extremely harsh cleaner that strips the hair and skin of natural oils. As well as stripping the natural oils from our skin.hair, both SLS and SLES can be absorbed into the skin. The chemicals have been found in the brain, heart, liver and other vital organs. No thanks…

There are another two derivatives which have larger molecules, large enough to not be absorbed into the skin, and are seen as milder alternatives again to SLS And SLES. These are Ammonium Lauryl Sulfate (ALS) and Ammonium Laureth Sulfate (ALES). However, they both strip the skin of natural oils in much the same way.

As the public became more aware of SLS/SLES, manufacturers have started using alternatives.  One such alternative is Sodium Myreth Sulfate, which is virtually identical to SLES.  There are even shampoos that claim to be sulfate free which contain Olefin Sulfonate. This is another foamer/cleanser that has been shown to be as irritable as SLS itself.

Another you may see is Triethanolamine Lauryl Sulfate (often labeled as TEA Lauryl Sulfate). It’s virtually identical to SLS without the same level of testing but is likely to be as irritable as SLS.

Is it any wonder people struggle to keep track of product labeling?  That’s why we’re here…


Alcohols in shampoos come largely in two forms. In one form, the alcohol will dry out your hair and scalp. In another form it will serve to condition your hair and scalp. Talk about confusing!

Alcohols classified as Short-Chain Alcohols will dry out your hair and scalp. These include Ethyl Alcohol, Ethanol, SD Alcohol, SD Alcohol 40, Alcohol Denat, Propanol, Propyl Alcohol, Propylene Glycol and Isopropyl Alcohol. Chemicals that are derived from these alcohols such as Isopropyl Palmitate can also irritate the skin.

Fatty alcohols won’t dry your scalp and are derived from much more natural sources such as coconut or vegetable oils. They are found in many moisturizing creams and conditioners as they actually moisturize rather than our skin. They include Lauryl Alcohol, Cetyl Alcohol, Myristyl Alcohol, Stearyl Alcohol, Cetearyl Alcohol, Oleyl Alcohol and Behenyl Alcohol.

There is another type of alcohol called Benzyl Alcohol that ought to be classified as a fatty alcohol but the manufacturers have found another synthetic means of creating it. The synthetic means of manufacture creates an alcohol that is extremely irritating to the skin. It should be on the good list, but it’s on the hit list!

Methylchloroisothiazolinone/Methylisothiazolinone (aka Kathon CG)

Methylisothiazolinone won the dubious title of Contact Allergen of the Year in 2013.  When combined with the equally unpronounceable Methylchloroisothiazolinone, the compound is known as Kathon GC. Kathon CG caused a storm in the UK in 2013 for causing an “epidemic” of contact dermatitis cases. It actually inspired me to write this blog as I was one of the sufferers! It’s a preservative found in many shampoos, creams, and cosmetics with such ill repute that the European cosmetics trade association told its members to remove MI from skin products. A number of manufacturers have already promised to remove this from all products, and until they do, Dandruff Deconstructed will be watching them like a hawk. This is a must avoid!

Cocamidopropyl Betaine

Made from coconut oil, Cocamidopropyl Betaine is a cleansing and lathering ingredient in a shampoo. It is a renowned allergen (either the ingredient itself or one of the compounds used to make the ingredient) and has the dubious honor of winning The American Contact Dermatitis Society Allergen of the Year in 2004.  It’s extremely tough to find a shampoo without it at the moment.


We all love fragrances, don’t we? They make us smell and feel nice. They are also among the most common cause of contact dermatitis in many of us and are added to many many shampoos. It seems such a shame that such a needless additive is causing so much damage to our scalps. The EU has a directive where 26 of the most common fragrances that cause reactions must be listed:

  • 3-Cyclohexane Carboaldehyde
  • Amyl Cinnamal
  • Anisyl Alcohol
  • Benzyl Alcohol
  • Benzyl Benzoate
  • Benzyl Cinnamate
  • Benzyl Salicylate
  • Butylphenyl Methylpropional
  • Cinnamal
  • Cinnamyl Alcohol
  • Citral
  • Citronellol
  • Coumarin
  • Eugenol
  • Evernia Furfuracea
  • Evernia Prunastri
  • Farnesol
  • Geraniol
  • Hexylcinnamal
  • Hydroxycitronellal
  • Hydroxyisohexyl
  • Isoeugenol
  • Isomethyl Ionone
  • Linalool
  • Limonene
  • Methyl-2-Octynoate

The EU list, good as it is, doesn’t go far enough though.  There are many other fragrances that can cause contact dermatitis including:

  • Alpha Amyl Cinnamic Alcohol
  • Anthemis Nobilis (Chamomile)
  • Balsam of Peru (Myroxylon Pereirae)
  • Cassia Oil
  • Chamomile (Anthemis Nobilis)
  • Cinnamon
  • Cinnamic Alcohol
  • Cinnamic Aldehyde
  • Citronella Candles
  • Citrus Limonum
  • Cloves
  • Ethylene Bassylate
  • Hydroxycitronellal
  • Lyral
  • Oak moss absolute
  • Phenoxyethanol
  • Yarrow (Achillea Millefolium)

Don’t trust the labels Fragrance Free or Unscented too. It just means there is no perceptible odour, but the manufacturers may well have added fragrance chemicals to achieve this!


Phthalates, a weird looking word pronounced thal-ates, is a group of chemicals that are used in many different industries. The chemicals are, broadly speaking, plasticisers that give materials an elastic, durable, malleable property. They are also used as a fragrance in some products. Do you know the smell of a new vinyl shower curtain? That’s phthalates. You’ll also find phthlates in wood finishes, detergents, adhesives, plastic plumbing pipes, lubricants, medical tubing and fluid bags, solvents, insecticides, medical devices, building materials, and vinyl flooring.   Woosh!

They used in many cosmetic products and they are a cause of contact dermatitis in some of us (as well as a number of other wider health hazards).

Silicone or Petroleum Oils

Manufacturers add silicone or petroleum products to “moisturize” your hair and scalp. They give it that lovely soft sheen that we all love. Although these aren’t strictly contact allergens or irritants, some silicone products typically aren’t water based and instead coat your scalp with a layer of oil. This prevents your skin from breathing and keeps sweat locked in. This can dry the scalp or even instigate eczema or psoriasis. There are a few different silicone/petroleum oils in shampoos:

  • Amodimethicone
  • Cetearyl Methicone
  • Cetyl Dimethicone
  • Cyclopentasiloxane
  • Cyclomethicone
  • Dimethicone
  • Dimethiconol
  • Dimethicone Copolyol
  • Mineral Oil (Paraffinum Liquidum)
  • Methicone
  • Petrolatum Liquidum
  • Phenyl Trimethicone
  • Stearyl Dimethicone
  • Trimethylsilylamodimethicone

We’ll warn you of the presence of any of them.

Ethylene Glycol/Polyethylene Glycol (PEG)

Ethylene Glycol, better known as anti-freeze to me and you, and Polethylene Glycol (PEG) are additives that give your shampoo the cleanliness, texture, sheen and viscosity we expect from luxurious hair products. On the flip side, both are known allergens in many folk.

Isopropyl Palminate

Derived from palm oil, Isopropyl Palminate is a moisturizer that can dry your scalp. Erm, how does that work exactly?

Cocamide DEA

This oil derived from coconuts is a surfactant that forms a cleansing agent in many shampoos.  Unfortunately it’s also a pretty severe source of contact allergens and in June 2012 the State of California listed Cocamide DEA as a chemical known to cause cancer. Wow!

Lauramide DEA

The main component of Cocamide DEA is Lauramide DEA; an ingredient that gives your shampoo a thick, stable foam. It is also a known irritant for some of us.


Lanolin is a wax or fat produced by sheep to protect and waterproof their wool. It’s used in many shampoos and conditioners for its moisturizing properties and in many of us it prevents dandruff. Confusingly though, for some of us it is an allergen. Avoid this if you’re allergic to wool, and be careful if you have seborrheic dermatitis as it seems to be a particularly prevalent allergen with that community. We’ll warn you of its presence in any of the shampoos we review.  So you can make an educated decision before buying.

Formaldehyde/Formaldehyde Releasing Preservatives

Formaldehyde is a renowned allergen which the EU has determined “may not be safe” in cosmetics. It’s one of the only ingredients I’ve seen score a 10 on the EWG Skin Deep Cosmetic’s Database. Perhaps not surprisingly, but still outrageously, you’ll see it in baby shampoos and soaps. You won’t see it listed as Formaldehyde though. It’ll be listed under a wide variety of names which are preservatives that release formaldehyde.

These include Quaternium-15, Dimethyl-Dimethyl (DMDM) Hydantoin, Imidazolidinyl Urea (Imidurea), Diazolidinyl Urea, Sodium Hydroxymethylglycinate and 2-Bromo-2-Nitropropane-1,3-Diol (bronopol). Who made up these names?

Butylated Hydroxytoluene (BHT)

BHT is an antioxidant used in a number of diverse products such as petroleum, rubber and embalming fluid.  There’s been a great deal of controversy about this preservative, not least because it can cause contact dermatitis. The European Food Safety Authority has labeled it a known human toxicant or allergen. That’s all we needed to know…


This muscle relaxant is also a preservative found in some shampoos. The major recognized side effect of this additive is allergic contact sensitivity. Why on earth do they add muscle relaxant to shampoos?

Tocopheryl Acetate

Added to many shampoos for its moisturizing properties, this chemical is essentially Vitamin E. Yay! Mixed with Acetic Acid. Nay! This can really irritate your scalp and is prevalent in many “organic” shampoos.

Potassium Sorbate

A preservative used to prevent mold or yeast growth.  You’ll see it in many skin products and foods, the most famous of which is probably McDonald’s Milk Shakes! Yummy!  Unfortunately, there is strong evidence that it can cause skin allergies on many folk.

The Ethanolamines

The Ethanaloamines are used in the manufacture of detergents and lubricants among others.  Triethanolamine (TEA), Diethanolamine (DEA), Monoethanolamine (MEA) are 3 of the most common Ethanolamines added to your shampoos. These chemicals give your shampoo its consistency and give the lather a rich texture. They are also known to irritate the skin of some people.

Tetrasodium EDTA

A strange chemical that makes hard water soft. The reason it’s in shampoos is that it’s much more difficult for a soap or shampoo to get you clean in hard water. So this agent makes the water softer while you’re washing. It’s also an irritant or allergen in some people, so we’re warning you of its presence. Many sites are reporting that it forms a far greater health hazard too, but I’m not the expert there.

Iodopropynyl Butylcarbamate

A preservative originally used to preserve paint and woods. Nowadays it’s found in cosmetics such as shampoos. Not surprisingly, a chemical used to preserve wood can cause contact dermatitis.

Sodium Hydroxide

Sodium Hydroxide aka Lye aka caustic soda is a relatively common ingredient in dandruff shampoos.  It controls the ph level of the shampoo, preventing it from becoming too acidic.  It’s also good at cleaning drains, removing paint, blackening olives and a whole host of other uses.  In small quantities it shouldn’t be a problem for most people, however, some people do react to it.  We’ll warn you if it’s in your shampoo so you can make an educated purchase decision.

Essential Oils

A number of recent shampoos use essential oils to combat dandruff rather than using a more traditional medicated approach.  Although data is limited, some of these essential oils e.g. Tea Tree oil are known to cause contact dermatitis.  In addition, some of the oils are highly fragrant and many contain linalool, limonene and other fragrances which themselves are known causes of contact dermatitis.   Where the data is available, we will warn of the presence of these fragrances when we are aware of them.

The Parabens

One of the most notorious chemicals in our shampoos, the Parabens (be that Propylparaben, Methylparaben, Butlyparaben, Ethylparaben, Isobutylparaben) are anti-bacterial agents added to shampoos to prevent the growth of mold. These aren’t strictly contact allergens at all but have been found to disrupt our hormones and have been found in cancerous tissues. Plenty of products are labeled paraben free these days and we will champion their cause until the full truth is found.

Cetrimonium Chloride

This preservative couples as a surfactant and has numerous names.  It’s also a known contact allergen so we’ll warn you about its presence, whatever guise it appears in.


Ethylhexyglycerin is one of the ingredients you’ll see in modern paraben free shampoos.  It serves a similar purpose in so far as its an anti-bacterial agent.  Unlike parabens, there it will not disrupt your hormones.  However, it has been shown in three separate studies to cause contact dermatitis in some individuals.





So that’s over 90 known contact allergens we’re looking out for with all shampoos we review. It’s almost a farce that some manufacturers are now flagging their product as SLS/SLES free when there are another 90 or so other allergens they could be warning you about. The EU is at least forcing manufacturers to list a number of these, but it’s still not enough. My life was a nightmare until I educated myself – I was allergic or irritated by so many of these chemicals. I may be an exception but I’m not that exceptional. There are plenty like me out there. And as far as we know, we provide the most comprehensive service out there for monitoring your shampoos for contact allergens.

It’s such a shame that we’re needed at all.

Show Comments


  1. Virginia Sheehan June 5, 2015
    • Chris Challis June 11, 2015
      • Blair April 7, 2016
        • Chris Challis April 7, 2016
        • Marmee June 28, 2016
          • Chris Challis June 28, 2016
          • Terry Green October 15, 2017
        • kate March 26, 2017
          • Chris Challis March 27, 2017
        • mar April 24, 2017
        • PandaBamboo June 9, 2017
        • mary June 27, 2017
          • Chris Challis June 27, 2017
      • melinda fillingim July 7, 2017
    • Anna Stewart June 23, 2017
  2. Janet November 16, 2015
    • Chris Challis November 16, 2015
  3. What Allergy? November 16, 2015
  4. Ms. CW December 13, 2015
    • Chris Challis December 18, 2015
  5. Debi Seligmann December 17, 2015
    • Darla Sneed June 3, 2016
    • Mary Estep August 9, 2016
  6. Ann Ponomarenko February 21, 2016
    • Chris Challis February 24, 2016
  7. dmg February 26, 2016
    • Chris Challis February 29, 2016
  8. Cindy March 18, 2016
    • Chris Challis March 18, 2016
  9. Marmee June 28, 2016
    • Chris Challis June 28, 2016
  10. Alexandria Peck July 23, 2016
    • Chris Challis July 23, 2016
  11. Faye September 28, 2016
    • Chris Challis September 29, 2016
  12. Nele Taevere March 21, 2017
    • Chris Challis March 21, 2017
  13. Tonya Llewellyn April 14, 2017
  14. Susan S May 13, 2017
  15. Sam June 9, 2017
  16. catherine July 4, 2017
  17. Terry Green October 15, 2017
  18. Mia January 26, 2018
  19. jeanne September 15, 2018
  20. Heather February 3, 2019
    • Chris Challis February 4, 2019

Leave a Reply

This site uses Akismet to reduce spam. Learn how your comment data is processed.