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All commercially manufactured hair products contain preservatives to inhibit the growth of bacteria, fungi and to protect the product from “spoilage.” Many can cause sensitivity and itching. These are commonly irritating preservatives:

Benzyl alcohol

Imidazolidinyl urea

Diazolidinyl urea

Sodium Hydroxylmethylglycinate

Methyl, Propyl, Butyl and Ethyl parabens

Phenoxyethanol

DMDM hydantoin

Quaternium-15

Methylisothiazolinone