Hydroxyacetophenone Best Antioxidant Anti-Ageing Hydration Hydroxyacetophenone at a glance Synthetic antioxidant and humectant Helps boost preservative systems in many types of formulas Noted for its soothing ability Considered safe as used in cosmetics (final report pending) Hydroxyacetophenone description Hydroxyacetophenone is a synthetic antioxidant and skin-conditioning ingredient. The specific antioxidant compound is actually known as p-hydroxyacetophenone, a phenolic antioxidant capable of neutralising several different types of free radicals. Its secondary benefit is boosting the preservation system in cosmetics. This is advantageous because it allows cosmetic chemists to use a lower amount of preservatives (such as phenoxyethanol) without losing efficacy but with the benefit of reducing the risk of an allergic reaction. Hydroxyacetophenone also has soothing ability because it can inhibit an enzyme (known as COX-2) in skin's surface that can lead to signs of irritation.