Resveratrol

Resveratrol is an antioxidant/anti-inflammatory polyphenol typically used around ~0.1–1% in leave-on serums, but it can be irritating in reactive or eczematous skin—especially because it’s often formulated in penetration-enhancing solvents (e.g., propanediol/ethoxydiglycol) that increase stinging risk. Human experience and patch/consumer use data suggest most tolerate it, yet a meaningful minority report burning/redness or dermatitis, so it is best categorized as mild rather than “gentle” for compromised barriers. Safety Notes: In consumer skincare, resveratrol is most often used in leave-on serums/creams at very low levels (around 0.001–0.05%) due to cost, oxidation/light sensitivity, and frequent pairing with synergists (e.g., ferulic acid, vitamin E) where only small amounts are needed. Mainstream antioxidant serums commonly sit around ~0.1–1%, while a small number of high-strength, direct-to-consumer “booster”/serum products reach about 2–3% (typically anhydrous, encapsulated, or otherwise stabilized to manage solubility and stability). Rinse-off products generally fall toward the lower end because short contact time reduces the incentive to formulate at higher levels.