What permanent damage can hair dye cause to the scalp or hair follicles?

From the Guidelines

Hair dye can cause permanent damage to the scalp or hair follicles, primarily through allergic contact dermatitis and chemical burns, which may lead to lifelong sensitivity, scarring, and hair loss. The most significant risk is associated with para-phenylenediamine (PPD), a common ingredient in hair dyes, as noted in a study published in Pediatrics 1. This chemical can trigger severe reactions, including facial swelling, blistering, and permanent scarring in sensitive individuals. Some key points to consider:

• Allergic contact dermatitis from hair dyes can lead to lifelong sensitivity to certain chemicals, particularly PPD.
• Chemical burns to the scalp can damage hair follicles beyond repair, resulting in permanent hair loss.
• Repeated use of dark dyes containing high concentrations of chemicals may lead to structural damage of the hair shaft itself, making hair permanently brittle, dry, and prone to breakage.
• To minimize risks, it is essential to perform a patch test 48 hours before application, follow product instructions carefully, avoid scalp contact when possible, and consider using semi-permanent or natural alternatives like henna if you have experienced previous reactions. The potential for permanent damage from hair dye is a significant concern, and individuals should be aware of these risks to make informed decisions about their hair care.

From the Research

Permanent Hair Dye Damage to Scalp or Hair Follicles

• There is limited research on the permanent damage that hair dye can cause to the scalp or hair follicles 2, 3, 4, 5, 6.
• Some studies suggest that permanent hair dyes may cause allergic contact dermatitis or irritant contact dermatitis due to ingredients such as ammonia and paraphenylenediamine (PPD) 6.
• However, a clinical evaluation of an ammonia-free and PPD-free permanent hair dye found no incidence of allergic or irritant contact dermatitis in 50 subjects 6.
• The same study found improvements in hair shine, color, moisturization, porosity, and combability after using the ammonia-free and PPD-free permanent hair dye 6.

Cancer Risk and Hair Dye Use

• Some studies have investigated the association between hair dye use and cancer risk, but the evidence is inconsistent 2, 3, 4, 5.
• A prospective cohort study found no significant increases in risk of solid cancers or hematopoietic cancers overall among ever users of permanent hair dyes 5.
• However, the study found a slightly increased risk of basal cell carcinoma and a positive association between cumulative dose and risk of estrogen receptor negative breast cancer, progesterone receptor negative breast cancer, hormone receptor negative breast cancer, and ovarian cancer 5.

Hair Dye Ingredients and Toxicity

• Hair dye ingredients have moderate to low acute toxicity, and human poisoning accidents are rare 4.
• In vitro genotoxicity tests on hair dye ingredients have frequently had positive results, but their correlation with in vivo carcinogenicity is uncertain 4.
• Studies in humans have found no evidence of genotoxic effects of hair dyes or their ingredients 4.