A fat-soluble antioxidant that mostly keeps a formula's oils fresh. It helps vitamin C protect skin, but on scars it doesn't help and often causes a rash.
Vitamin E is a family of fat-soluble antioxidants. Tocopherol is the active form; tocopheryl acetate is a more stable ester that skin has to convert, and it does so only slowly. On most labels it sits at well under 1%, where its job is to stop the product's plant oils going rancid — useful, but a job for the bottle rather than your skin.
Its clearest role on skin is as a partner: applied with vitamin C (and ferulic acid) it adds to protection against UV-triggered redness and damage. On its own, the popular uses — fading scars, healing wounds, preventing stretch marks — have not held up in trials.
Lab and small human studies show tocopherol reaches the skin and, combined with vitamin C, reduces UV-induced redness and sunburn cells. Controlled evidence that vitamin E alone improves wrinkles or scars is thin, and a small double-blind scar trial found no benefit and frequent allergic reactions. None of this makes vitamin E a sunscreen.
15 patients applied a plain emollient to one half of a surgical scar and the same emollient with vitamin E to the other half for 4 weeks; vitamin E had no effect or worsened appearance in 90% of cases, and 33% developed contact dermatitis.
A literature search found 931 reported cases of vitamin E allergic contact dermatitis, mostly from one large study; the authors judged it uncommon relative to how widely vitamin E is used in skin care.
Adding ferulic acid to a 15% L-ascorbic acid + 1% alpha-tocopherol solution improved its chemical stability and doubled its protection of skin against solar-simulated UV (from about 4-fold to about 8-fold), measured by redness and sunburn cells; thymine dimer formation was also reduced.