In a Sponsor-Funded UV Test, an Encapsulated Vitamin C Serum Did No Better Than Bare Skin

A trial published in the May 2026 issue of the Journal of Clinical and Aesthetic Dermatology tested how well two serums protect skin against a dose of ultraviolet light. One was a multi-antioxidant serum, which the authors call TAP. The other was an encapsulated vitamin C serum. The study was sponsored by skinbetter science, a dermatological brand of L'Oréal USA, and the formula described for TAP matches the one skinbetter sells.

The design was simple and short. Sixteen healthy women aged 35 to 60 with fair to light-medium skin took part, and fifteen finished. Each person had four marked areas on the lower back. Clinic staff applied one serum to one area and the other serum to a second area once a day for four days. A third area was left untreated but exposed to UV, and a fourth was neither treated nor exposed. On day four the areas were given one and two times each person's minimal sunburn dose, then photographed and biopsied the next day.

According to the paper, the multi-antioxidant serum produced clearly less redness than both the vitamin C serum and the untreated area, for example 72% less than the vitamin C serum at the lower UV dose. It also lowered several markers of UV damage in the biopsies, including DNA damage, sunburn cells and immune cell counts. The encapsulated vitamin C serum showed no significant difference from untreated skin on redness or on any marker.

A few cautions apply. The sample is small, the skin was on the back rather than the face, and four days of use followed by one UV dose says nothing about long-term brightening or ageing. The paper does not name the vitamin C product or give its strength or form, so the result cannot be applied to vitamin C serums in general. Some p-values and percentages differ between the abstract and the main text, and some reductions are given as more than 100%, which the paper does not explain. Two authors work or worked for the sponsor's group, and the investigators were employed by the contract lab the sponsor paid.

What the result does support is a familiar point: an antioxidant serum is not a substitute for sunscreen, and the word encapsulated on a label is not proof that a product protects skin.