nner-most
             layer of the epidermis, through the middle layers, out toward the surface of
             the skin where they die. This surface layer (or stratum corneum) forms a tough
             outer protective covering. As the cells move outward, they lose moisture, flatten
             and eventually flake off the surface of the skin. This process takes about 28 days.
             Tanning: There are two effects that occur in the skin following exposure to UV
             radiation. When the skin is exposed to ultraviolet radiation a slight, immediate
             pigment darkening or immediate tanning is sometimes observable. It is believed
             to result from darkening of the melanin pigment that is already present in the
             epidermis as it absorbs and filters out some of the damaging UV radiation. This
             tan is only temporary, and fades within 3 to 36 hours after exposure. This type of
             tan is strongly stimulated by UVA radiation.
             A second process known as "delayed tanning" occurs in some individuals when
             the skin is exposed to ultraviolet radiation. This process causes two responses. a)
             more melanocytes (skin cells capable of producing melanin pigment) are produced
             at the base of the epidermis, and each melanocyte produces more melanin pigment.
             These melanin-containing cells begin to distribute themselves throughout the
             layers of the skin, as they work their way toward the surface of the skin. This
             greater presence of melanin-containing cells causes the skin to appear darker in
             colour. b) the tough outer or surface layer of dying skin cells thickens and absorbs
             more of the hazardous shortwave UVB radiation, thereby increasing protection
             to the inner living skin tissue from the harmful rays. This second, two-part process
             takes one or more days to happen, and produces a noticeable tan within a few
             days that can last for weeks or even months.
             Ultraviolet Radiation (UVR) is a form of electromagnetic energy with
             wavelengths ranging from 100 to 400 nanometres. These w...