Why does my tan fade?

Since a tan occurs in the epidermis, the skin’s outermost layer, it is eventually lost during the natural exfoliation process. Skin replaces its cells about every 30 days; when the cells in the top layer are exfoliated, allowing new ones to reach the surface, they take with them the darkened melanin created by the exposure to UV light. At this point you have tanned melanin both in your skin and on the surface of your skin. Tanned melanin on the surface of the skin is going to remain there only until you shave or exfoliate it off. Of course regular tanning visits rebuild what has been lost.