Fragrances are still the #1 allergen in cosmetics, causing the most allergic reactions. While restrictions on preservatives like formaldehyde have helped reduce some problems, new allergens are popping up in sunscreens, hair dyes, and natural ingredients—and these are catching both consumers and doctors off guard.

This is a 2025 review that analyzed existing research on cosmetic allergies, looking at which ingredients trigger reactions most often and how doctors currently diagnose and treat them.

Funding not disclosed in abstract