Shampoo Allergy: Top Allergens

#4 Formaldehyde Releasers

Formaldehyde-releasers (FDRs) are the fourth most common allergen in shampoos. Studies by Zirwas and colleagues showed that 48.6 % of shampoos contained FDRs. 
FDRs are used as antimicrobial and antifungal preservatives in a wide variety of cosmetics and hair care products. They are called “releasers” because these chemicals slowly release the chemical formaldehyde as they break down and such release can cause irritation or allergic contact dermatitis.

In the right circumstances these FDRs can release formaldehyde in concentrations exceeding 200 ppm.

There are well over 40 FDRs but the 7 most common are: 
DMDM hydantoin
Imidazolidinyl urea
Diazolidinyl urea
Quaternium-15
Bronopol
5-Bromo-5-nitro-1,3-dioxane
Sodium hydroxymethylglycinate
 

Reference

de Groot A, et al. Contact Dermatitis. 2010.

Zirwas et al. Dermatitis 2009.