A researcher at Johnson and Johnson Inc. has conducted a study that may pave the way for Johnson and Johnson to start putting vitamin D in their skin care products; in particular, their products for dry skin or xerosis.
Dry skin, which often occurs during the winter, is commonly treated with emollients and/or moisturizers. Xerosis occurs most commonly on the scalp, lower legs, arms, the knuckles, the sides of the abdomen and thighs. When severe, symptoms can include peeling of the outer skin layer and cracking.
Activated vitamin D analogs have been shown to increase expression of a protein called filaggrin in the skin. Filaggrin is intimately involved with keeping the skin moist and those without the gene for filaggrin often have very severe eczema.
Dr Meghan Russell of Johnson and Johnson wanted to know if plain nutritional vitamin D had an effect on dry skin, and investigated a few things.
First, she took 83 subjects likely to have dry skin and measured their vitamin D levels. Sure enough, she found that the lower the vitamin D levels, the drier the skin.
Second, she added plain vitamin D3 to skin moisturizers in half of 61 subjects and compared that group to a placebo group that only got the moisturizers. That is, in her second study, vitamin D was applied directly to the skin. Sure enough, she found less dry skin in the group treated with topical vitamin D than with the usual moisturizers.
Although she did not make the topical dosage of vitamin D clear, it appeared that the vitamin D group only put 400 IU on their lower legs every day for three weeks, so her results probably were not due to raising vitamin D blood levels. Rather, there may have been some kind of direct action working locally on the skin. Still, her first study suggested that higher vitamin D levels would mean less dry skin.
The question still remains if vitamin D can be absorbed topically. I am unable to find any studies that tested the idea that topical vitamin D is absorbed through the skin. I suspect some is, but the outer layer of the skin can be difficult to penetrate. I also suspect you will find your dry skin is much better by simply taking 5,000 IU per day by mouth than messing around with topical applications of vitamin D, though we still need more research to clarify these issues.