When we sit in the sun, our skin gets a nice brown color (or sometimes a less beautiful red color!). How come? And is it due to the same process that self-tanning day creams and ‘tanning without sun’ tubes start to color our skin?
Answer
Our skin will turn browner under the influence of sunlight (UV-B rays). In a first phase, sunlight will cause the oxidation of melanin (pigment) in the skin. In a second phase, the melanocytes in the skin will produce more melanin and deposit it in the keratinocytes (skin cells). This new melanin ensures a longer lasting tan. The amount of melanocytes in the skin can vary from person to person, but the difference in color is attributed to the amount of melanin they produce rather than the number of melanocytes.
UV-B rays strike the outer layer of skin cells (keratinocytes) and thus stimulate the production of MSH (melanocyte-stimulating hormone). MSH reaches the melanocytes and causes the production of melanin, which then settles in a new layer of keratinocytes.
Tanned skin offers greater protection against sun damage and cancer. Among other things, to protect people with light skin against this, all kinds of remedies are being developed to give them a brown skin without UV-B exposure. Some of these remedies contain substances that stimulate the production of MSH. Other remedies contain a substance that presumably affects the gene expression of melanocytes, and still others probably only put a layer of ‘paint’ on the skin.
Answered by
dr. Peter Strager
Molecular Microbiology Biomedical Sciences Medical and pharmaceutical research Molecular Biotechnology
http://www.ugent.be
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