Tannic Acid

Tannic acid is a polyphenolic astringent used for its antimicrobial/anti-inflammatory and oil-controlling effects, but at typical topical use levels (often ~0.1–2%) it can be notably drying and protein-precipitating, which increases stinging and barrier disruption risk in eczema-prone or compromised skin. Patch testing and clinical experience show tannins can provoke irritant reactions and, less commonly, contact allergy, especially with repeated exposure or when layered with other actives. Given its functional astringency and sensitization potential in sensitive populations, it warrants a significant irritation score and cautious introduction. Safety Notes: In modern OTC skincare, tannic acid is most often used as an astringent/antioxidant at very low levels (commonly around 0.01–0.1%) in leave-on toners, serums, and anti-blemish/anti-redness products to manage sensory harshness and staining. Higher-strength consumer products (not prescription/pro-only) include strong astringent “pore-tightening”/aftershave-style lotions, foot/anti-odor preparations, and some specialty deodorizing or anti-sweat cosmetics where tannic acid can reach the low single digits; the upper end observed is about 5% in OTC products, above which irritation and instability become limiting.