The Role Of The Skin

Overexposure may cause acanthosis, or thickening of the horny layer, which can give a person a dull look. Clients of indoor tanning salons should receive a dose that neither overexposes nor underexposes them to UVR. No one should be allowed to tan for longer than the approved MTI (maximum timer interval) of the tanning unit.

In order for the pigmentation process to be effective, melanin granules must be oxidized or darkened, which requires a high dose of long-wave UVA. A sufficient amount of energy must be provided to initiate the oxidation process. UVB causes quickening of the migration of germ cells to form a thicker horny layer. In short, UVB synthesizes pigment granules, while UVA only ensures their oxidation. Together, the two form a light-protection mechanism.

Please note that a tan produced by UVA light alone only gives the illusion of light protection because the skin appears to be more tanned. Actually, neither a thickening of the skin nor pigmentation has taken place, which means the skin is as vulnerable to ultraviolet light as before.

Melanin is the leading factor that determines a person’s skin color, and its presence is determined by hereditary factors. This is based on the regions of the world from which a person’s ancestors came and is referred to as constitutional skin color. But not all skin color is based on constitutional skin color. Facultative skin color, referred to as tanning, is the result of deliberate exposure to ultraviolet radiation. Here, hormonal factors determine the shade of a tan one will develop.

Each skin type reacts in its own way to UV radiation. The reaction is dependent upon the amount of pigment already in the skin naturally, the capability to build up additional protection (facultative pigmentation) and the degree of thickening of the uppermost horny skin layer (acanthosis).

All of these factors are determined genetically. In the initial stage of tanning, the skin has what are called pre-pigment grains that appear gray-brown in color. The visible result of these grains is immediate tanning, seen in people who tan easily. However, this color can disappear very quickly, in as few as 24 hours. In the lowest layer of the outer skin, the melanocytes (melanin-producing cells) begin to generate new pigment grains called melanosomes. Because this is a slower process than the immediate tanning of pre-pigment grains, it is known as indirect pigmentation. With the presence of UVB, melanocytes are stimulated to divide, creating more pigment cells. During this time, the epidermis thickens to form additional protection, again a condition referred to as acanthosis.

The actual production of melanin occurs deep within the outer skin where melanocytes are situated. Melanocytes are capable of growing between the surrounding keratinocyte cells and forming offshoots called dendrites. It is at this point that melanocytes have the ability to be stimulated by UV rays to achieve their purpose of producing melanin. Eventually, the pigment grains change from their initial pink color to their final stage of reddish-brown or a tan. The peak color that can be achieved is dependent upon an individual’s tanning schedule and individual factors such as skin type, hormonal influences and recent UV history.

Melanin can compensate for only so much UV light. It’s not difficult to spot a tanner who has had too much UV exposure. Photo-induced inflammation, better know as a sunburn, is the result of an overdose of UVB rays. Longer wave UVA produces a reddening of the skin only when sufficient photosensitizing effects are taking place, due to an excess dosage or a high concentration of photosensitizing substances, such as certain medications, perfumes or lotions. A sunburn resulting from too much UVB causes cell damage on only the top germinative layer where cells eventually flake off. A sunburn from UVA, however, reaches deep into the connective tissues, permanently damaging the delicate elastic fibers of the skin.