Menthol

Menthol is a cooling counterirritant/fragrance component typically used around ~0.05–1% in leave-on products and higher in some rubs; it activates TRPM8 and can produce burning, stinging, and barrier disruption despite a “soothing” sensation. Clinical experience and patch-test data show it is a common trigger for irritation and can exacerbate eczema/rosacea, with higher risk when combined with other actives or on compromised skin. Given its frequent symptomatic irritation in sensitive populations and potential to worsen dermatitis, it merits a high irritancy score. Safety Notes: In mass-market skincare and personal care, menthol is often used at trace-to-low levels (~0.01–0.3%) in leave-on products (e.g., lotions, aftershaves, acne/toning products) to add a mild cooling sensory effect without excessive irritation. Many rinse-off cleansers, shampoos, and shower products commonly sit around ~0.1–1% for a noticeable cooling profile. The upper end observed in OTC consumer-available topical analgesic/cooling balms and rubs (sold broadly at retail) reaches about 10% menthol; higher levels are uncommon in cosmetic skincare due to strong irritation/sensitization potential and sensory intensity, and are more typical of drug/analgesic-type rub formats rather than facial leave-on skincare.