Shampoo Allergy: A Closer Look at Propylene Glycol

Propylene Glycol as a Shampoo Allergen

Propylene glycol is an ingredient commonly found in shampoos and cosmetic products in general. It acts as a solvent for many other ingredients including preservatives, fragrances and chemicals. It also acts as a humectant (meaning that it attracts water), and has some antimicrobial properties.

PG can act as an irritant and sometimes a true allergen. Irritant reactions are far more common; however allergic reactions have been well appreciated for several decades.

Studies by Zirwas and colleagues showed that propylene glycol was the fifth most common allergen in shampoos - found in 38 % of surveyed shampoos.
 

Reference

Skin reactions to propylene glycol.
Hannuksela M, et al. Contact Dermatitis. 1975.

Zirwas M, et al. Shampoos. Dermatitis. 2009