Diethylhexyl Syringylidenemalonate

Diethylhexyl Syringylidenemalonate is a lipophilic antioxidant/photostabilizer used at low concentrations (typically well under 1–2%) to help reduce photo-oxidative stress and improve stability of formulas. Available safety and cosmetic use data suggest a low rate of irritation in standard patch testing, with irritation risk mainly tied to individual sensitivity or compromised barriers rather than inherent reactivity. For severe eczema or post-procedure skin I still treat it as “very gentle” rather than inert, since any nonessential lipophilic additive can rarely provoke stinging or dermatitis in highly reactive patients. Safety Notes: Diethylhexyl Syringylidenemalonate (Oxynex ST) is used as a multifunctional antioxidant/photostabilizer and is typically dosed low (about 0.05–0.3%) in mass-market sunscreens and daily moisturizers to support UV filter stability and reduce oxidative stress without impacting sensorial profile. In consumer-available high-antioxidant serums, premium sunscreens, and anti-pollution/anti-aging leave-on products, it is observed up to ~1–3% as part of boosted antioxidant systems; rinse-off products, when present, tend to stay at the lower end due to cost and limited contact time.