Propylene glycol dermatitis.

Propylene glycol is a super common ingredient in skincare and cosmetics, but it can cause two types of skin problems: irritant reactions (where your skin gets red and uncomfortable) and allergic sensitization (where your body develops an allergy to it over time). The research shows these reactions are real and documented enough that dermatologists need to screen for propylene glycol sensitivity in patients with unexplained skin issues.