It is not irritating as it does not contain pure L-Ascorbic acid. We use an oil soluble which penetrates more efficiently, protects the lipid membranes, including epidermal lipids (preventing superficial photo damages). Because it has deeper penetration abilites, is treats deep photodamages (reducing the dermal radical load), strenghtens blood capillaries, and reduces radical protein content in the ECM. (protection from loss of elasticity / assist in firming)