Phloretin

Phloretin is a polyphenol antioxidant typically used around ~0.5% in serums, often in hydroalcoholic or acidic vitamin C systems that can amplify stinging on compromised skin. While it is not a classic high-risk allergen, clinical experience and patch-testing patterns with antioxidant blends show occasional irritation in reactive/eczema-prone users, especially when layered with other actives. Given its common formulation context and the need to protect highly sensitive patients, a mild irritation score is warranted. Safety Notes: In commercial skincare, phloretin is most often used as a leave-on antioxidant active at low levels (commonly 0.3–1.0%) due to solubility/oxidation limits and frequent pairing with vitamin C/E/ferulic; at the low end, it appears in multi-antioxidant or brightening serums/creams where it is a supporting ingredient around 0.01–0.1%. The highest consumer-available products observed push to about 2% in anhydrous or high-solvent systems (e.g., alcohol/propylene glycol) to maintain solubility and stability; higher than this is uncommon in OTC due to formulation challenges rather than specific regulatory caps. Rinse-off products tend to use lower levels than leave-on because of limited contact time and cost/solubility considerations.