Hydroxyacetophenone

Hydroxyacetophenone is primarily used as an antioxidant/preservative booster and soothing adjunct, typically around ~0.3–1%, and is generally well tolerated but not truly inert. Patch-test and real‑world reports show occasional irritation or sensitization, especially in compromised barriers (eczema/post‑procedure) and when layered with other actives, so I score it as mild rather than “gentle” for patient-safety. Safety Notes: Hydroxyacetophenone is most commonly used in consumer leave-on and rinse-off products as an antioxidant/preservative booster and soothing co-ingredient, with low-end commercial use around 0.05–0.1% (often in formulas aiming for minimal additive load). In real-world OTC products it is frequently found at ~0.2–0.5%, while high-strength consumer-available formulations (especially “preservative booster” or sensitive-skin oriented leave-ons) reach about 1.0%; levels above ~1% are uncommon in mainstream retail due to diminishing benefit and greater risk of sensory/irritation tradeoffs.