Shampooing cheveux gras — ingredient safety report

• Irritation:Drying and barrier-disrupting in high-alcohol formulas with regular use.

Denatured ethanol gives products a fast-drying, weightless feel, but as a leading ingredient it degrades the skin barrier with repeated use — a poor match for dry, sensitive or eczema-prone skin.

• Allergy risk:Fragrance is the single most common cause of cosmetic contact allergy.
• Irritation:Frequent trigger of stinging and redness on reactive skin.

An umbrella term that can hide dozens of undisclosed scent chemicals. Fragrance is the leading cause of allergic contact dermatitis from cosmetics, and dermatologists routinely advise fragrance-free products for eczema, babies and sensitive skin.

• Allergy risk:The most common cause of sunscreen photoallergy.
• Environmental impact:Linked to coral bleaching; banned in Hawaii and other reef regions.

The most controversial chemical UV filter: a top cause of sunscreen allergy, a suspected endocrine disruptor found in blood and breast milk, and banned in several reef jurisdictions for coral toxicity.

• Allergy risk:Potent sensitizer, typically blended with MIT (Kathon CG).
• Irritation:Corrosive in concentrate; irritating at use levels.

The chlorinated partner of MIT, restricted in the EU to rinse-off products only. A leading cause of preservative contact dermatitis worldwide.

• Allergy risk:Caused an epidemic of contact allergy; banned in EU leave-on products.
• Irritation:Irritating even in people without allergy.

A preservative behind one of the largest contact-allergy epidemics in cosmetic history. The EU banned it from leave-on products and restricts it in rinse-off products to 15 ppm.

• Irritation:Milder than SLS but still drying for compromised skin.

The gentler cousin of SLS used in most mainstream shampoos and washes. Its manufacturing can leave trace 1,4-dioxane, which reputable makers strip out — an issue of quality control rather than the ingredient itself.

• Allergy risk:Named Allergen of the Year 2004; impurities (amidoamine) drive most reactions.

A mild coconut-derived surfactant in countless 'gentle' cleansers. Most allergy is caused by manufacturing impurities, so quality varies by brand.

• Allergy risk:One of the 26 EU-declarable fragrance allergens.
• Irritation:Mild irritation possible at higher concentrations.

A preservative and fragrance component that must be declared on EU labels because it can trigger contact allergy in a small share of users.

• Environmental impact:Poorly biodegradable; can remobilize heavy metals in waterways.

A metal-binding stabilizer that is safe on skin at the tiny amounts used; its criticism is environmental persistence.

• Allergy risk:Rare hypersensitivity reactions, better documented in food than cosmetics.

Tartrazine yellow dye; approved for cosmetics with rare sensitivity reactions reported.

• Irritation:Can cause transient, non-allergic flushing/stinging on reactive skin.

A food-grade preservative generally regarded as one of the gentler options; occasional non-immune stinging is its main drawback.