Vitamin C serum is used to treat wrinkles, scars and fine lines. A great many skin-care products exist that contain only Vitamin C derivatives. Facial allergic reactions to products containing Vitamin C serum do occur and those with sensitive skin should be cautious with this ingredient.
Vitamin C used in skin-care products is an unstable ingredient. When exposed to air Vitamin C (L-ascorbic acid) goes through oxidation and becomes ineffective and potentially harmful.
Oxidized Vitamin C may increase the formation of free radicals. These can irritate, harm and aggravate the skin, causing allergic reactions, rashes and burns. Some newer facial products containing Vitamin C derivatives are effective with lower concentration levels.
Vitamin C products that claim to be highly potent are highly acidic. These act as an exfoliating product and can be harsh, causing adverse reactions and/or allergies on some skin types.
Face serums containing Vitamin C may include only Vitamin C derivatives such as magnesium ascorbyl phosphate or ascorbyl palmitate. These can cause adverse reactions to the skin. L-ascorbic acid is the only useful and beneficial form of Vitamin C for winkles, scars and fine lines.
Vitamin C skin serum does not work for everyone, can cause cause allergic reactions in some and may include other ingredients that have no benefit or may be harsh on the skin. Concentration of Vitamin C is a key ingredient for effectiveness.
Yellowing of serum can indicate oxidation and ineffectiveness. Tinted products hide oxidation. Vitamin C serums that are oxidized are useless and may cause damage and allergic reactions to the skin.
References and ResourcesCleveland Clinic: Understanding Ingredients in Skin Care Products
Smart Skin Care: Vitamin C skin benefits
Vitamin C Serum By Dr. Jo