Because UV-A rays penetrate clouds, window glass and most clothing materials, we are constantly at risk to lose the normal levels of vitamin A in the skin. One thing is sure, the repetitive exposure of skin to sunlight results in lowered skin levels of vitamin A and C etc each day and that, unfortunately, is not corrected each day by the body. The impairment of vitamin A activity in the skin results in inadequate function of the Langerhans cells and as a result allergic problems of skin are more likely in sun-damaged skin than in protected skin. That is the reasoning behind using vitamin A as a therapeutic agent in skin atopy. Beta-carotene can be broken down in cells to two molecules of retinaldehyde, which in turn can be transformed into retinoic acid or retinol.
Retinoic acid is the form of vitamin A that does all the work in the nucleus.
There are various retinoic acid receptors that act as ligands and promote numerous genes responsible for normal skin. Without a doubt, in skin atopy there is also a massive onslaught of free radical activity that has to be addressed in order to allow the natural forces of the body to begin their repair work. Vitamin C is probably the most powerful antioxidant to stabilise cellular membranes. This is a paradox because vitamin C is water-soluble and cellular membranes are lipophilic. Vitamin E is also essential for the stabilisation of lipids.