Vanillin

Vanillin is primarily used as a fragrance/flavor component in cosmetics, typically at low concentrations, but it can still provoke irritation in highly reactive or barrier-impaired skin. Fragrance-related ingredients are overrepresented in patch-test positives and can cause both stinging/irritant dermatitis and, less commonly, allergic contact dermatitis, especially in eczema patients. Given the high-risk sensitive-skin population and the fact it provides no barrier or therapeutic benefit, a moderate irritancy score is warranted with patch testing advised. Safety Notes: In mass-market leave-on skincare and body care, vanillin is typically used as a fragrance component or flavor/aroma note at trace levels (often ~0.0001–0.01%), especially in products labeled “vanilla-scented” where it supports the parfum accord. Higher levels are seen in strongly scented consumer products (e.g., body lotions, body butters, lip balms, and some rinse-off washes/scrubs) and in “fragrance-forward” or DIY-style formulations where vanillin can reach ~0.1–1.0%, with practical limits driven by solubility, color/odor impact, and oxidation/discoloration risk (more noticeable in leave-on systems).