Topical vitamin C is L-ascorbic acid in a serum or cream put on the skin. It is an antioxidant, and vitamin C is also needed to make collagen. It is a skin-care product, separate from vitamin C taken by mouth.
Also known as: vitamin C serum, L-ascorbic acid serum, ascorbic acid cream.
Serums are labeled by percent. Trials used a 5% vitamin C cream daily for 6 months (Humbert 2003) and 3 drops (0.5 mL) of an ascorbic acid serum daily for 3 months (Traikovich 1999). These are study protocols, not a recommendation.
How it gets in: in a study on pig skin, L-ascorbic acid entered the skin only when the product was below pH 3.5, absorption was best at 20%, skin levels were saturated after 3 daily applications, and related forms (magnesium ascorbyl phosphate, ascorbyl palmitate, dehydroascorbic acid) did not raise skin vitamin C (Pinnell 2001). So the form and the formula matter.
What studies show: in a 6-month double-blind trial in women with sun-damaged skin on the neck and arms, 5% vitamin C cream improved overall scores, skin texture and deep furrows more than the cream base alone, and was well tolerated (Humbert 2003). In a 3-month split-face trial in 19 people aged 36 to 72, the side treated with ascorbic acid serum improved more than the side treated with the serum base on skin texture measures and on fine wrinkles and roughness (Traikovich 1999).
Both trials were small. See vitamin C for the vitamin taken by mouth.
We found no published half-life or time to peak for vitamin C put on the skin, so we do not list one. In the pig-skin study, vitamin C left the skin with a half-life of about 4 days after it was saturated (Pinnell 2001), but that is a skin-tissue figure in animals, not a blood half-life in people.
How Dose Track handles peptides · Reconstitution calculator · Half-life calculator