Hydroxyapatite

Hydroxyapatite is a biocompatible calcium phosphate mineral used mainly as an opacifying/abrasive or remineralizing agent (commonly in oral care and some topical products) and is generally well tolerated at typical use levels. Clinical and patch-test experience suggests low inherent irritancy, but as an insoluble particulate it can cause mild mechanical irritation on compromised or highly reactive skin, especially with friction or in leave-on products. Given sensitive-skin safety considerations, it is best classified as very gentle rather than fully inert. Safety Notes: In skincare, hydroxyapatite is most often used as a bioactive/skin-identical mineral or opacifying/soft-focus powder in leave-on creams/serums at low levels (typically around 0.1–1%), with the lowest observed commercial usage around ~0.05% as a supporting/minor claim ingredient. The highest consumer-available levels are found in mineral-powder-heavy products (e.g., masks, balms, body products, blur/primer-style creams) where hydroxyapatite functions as a primary particulate filler/texture agent; these can reach roughly 10–15% while remaining OTC and cosmetically stable. Rinse-off facial cleansers and wash-off masks generally sit in the mid-range, but the market maximum is driven by high-solids leave-on or wash-off paste-like formats rather than conventional emulsions.