The 12 Ingredients to Avoid on Any Shampoo Bottle

The average shampoo contains between 20 and 30 ingredients. Most are applied to the scalp, which has one of the higher absorption rates of any skin surface due to its high density of hair follicles. Products that remain on the scalp longer, including leave-in treatments and dry shampoos, have more absorption potential than rinse-off shampoos. What goes on your scalp, in meaningful amounts, enters your bloodstream.

Why shampoo is a high-priority swap

Hair washing is a daily or near-daily routine for most people. Cumulative exposure from repeated application of a product containing endocrine-disrupting chemicals matters more than single-use exposure. The scalp also differs from body skin in that hair follicles create direct channels to the dermis, bypassing the normal barrier function of the stratum corneum. A 2018 study in Reproductive Toxicology found that women who used hair relaxers and other leave-in hair products had higher urinary phthalate metabolites than those who did not, consistent with scalp absorption.

The 12 ingredients to look for and avoid

The twelve: (1) Fragrance or parfum, a blanket term covering potentially hundreds of undisclosed compounds including phthalates. (2) Parabens: methylparaben, ethylparaben, propylparaben, butylparaben. These are oestrogen mimics found in breast tumour tissue. (3) Sodium lauryl sulfate (SLS): a foaming agent that strips the scalp of natural oils and may increase skin permeability. (4) Sodium laureth sulfate (SLES): gentler than SLS but may be contaminated with 1,4-dioxane. (5) DMDM hydantoin: releases formaldehyde. (6) Cocamide DEA, MEA, TEA: may form nitrosamines, classified as probable carcinogens. (7) PEG compounds: potential 1,4-dioxane contamination. (8) Benzophenone and derivatives: oestrogen mimics used as UV stabilisers. (9) BHT and BHA: synthetic antioxidants linked to endocrine disruption. (10) Coal tar dyes: listed as CI followed by a number, potential carcinogens used for colour. (11) Phthalates: often hidden within fragrance listings. (12) Triclosan: antibacterial agent linked to thyroid disruption, banned in some countries.

“The scalp has hair follicles that create direct channels to the dermis, bypassing normal skin barrier function. What you apply to your scalp daily absorbs at a higher rate than most body skin.”

How to read a shampoo ingredient list

INCI stands for International Nomenclature of Cosmetic Ingredients. All cosmetics sold in the EU and US must list ingredients in INCI order, from highest concentration to lowest. The first five ingredients make up the majority of the formula. The most concerning ingredients are often preservatives and fragrance fixatives found towards the end of the list; they are present in small quantities but are applied daily. Use the EWG Skin Deep app to scan a product barcode and get instant ingredient hazard scores.

The transition period

Switching from sulphate shampoo to a clean alternative often involves a 2 to 4 week adjustment period during which the scalp overproduces oil as it recalibrates from years of oil-stripping washes. This is temporary and normal. Washing less frequently during this period helps. Some people find co-washing (conditioner-only washing) useful during the transition. The scalp normalises.

What to use instead