The Anatomy Of A Tan

The Anatomy Of A Tan
Ultraviolet Light And The Tanning Process

by Amy Thorlin

Salon operators should fully understand the tanning process, and relay the information to clients in an understandable and informative manner. Education is a key to ensuring that sensible, moderate and responsible tanning practices are followed.

The skin is an amazing organ, and it is the salon operator’s responsibility to help ensure its protection. The skin of an average person weighs eight to 10 pounds and covers an area of approximately 22 square feet. The skin performs a number of important functions: It protects the body against injury, is a first line of defense against invading organisms, helps to maintain the body’s internal temperature, and stores water, fat and vitamins.

The skin can be divided into three main layers. The subcutaneous layer is the deepest layer of the skin and provides insulation and food reserves, contains large blood vessels and nerves, and binds the skin to the body. The dermal layer is the middle layer and contains small blood vessels and nerve endings. This layer also contains collagen that provides strength and durability, and elastin that allows the skin to stretch and come back into place.

If collagen and elastin are depleted, premature aging, sagging and wrinkling of the skin can occur. In fact, if collagen is depleted to a certain point, the skin can tear like paper.

The outermost layer of the skin, the epidermis, is where the entire tanning process takes place. The epidermis is made up of roughly 5 percent melanocytes, 90 percent keratinocytes and 5 percent Langherans cells and Merkel cells. Langherans cells, also known as “immune cells,” help fight off organisms trying to invade the body. Merkel cells, known as “touch receptors,” relay touch sensations to the dermis as contact nerve endings.

The layers of the epidermis involved in the tanning process are the horny (outer) layer and the germinative (inner) layer. The outer surface of dead cells (horny layer) is the first shield against any invader. These cells, called keratinocytes or skin cells, produce keratin, a tough fibrous protein. Keratinocytes arise from the living dividing basal cells and are named for their location at the base of the epidermis. New cells rise, pushed from the base by rapidly dividing basal cells. It takes approximately four to five weeks for the cells to make their way to the surface.

Melanocytes,which are the pigment cells involved in the tanning process, exist at the base of the epidermis. The melanocytes produce melanin (pigment) when oxidized by UVR, providing the adaptive coloration of the skin. Melanin is made from an amino acid called tyrosine. The melanocytes are spider shaped and have many arms that reach all of the keratinocytes in the basal layer. The melanin then is transferred from the melanocytes to the keratinocytes. The melanin accumulates on the surface of each keratinocyte, creating a shield around the nucleus.

All individuals have roughly the same number of melanocytes, but heredity determines how much melanin can be produced. The skin of a person with higher skin type (genetically darker skin coloring) contains more melanin than that of a person with a lower skin type (lighter coloring). Every individual has only a given amount of melanin, which is determined by skin type. Although a person gradually may increase the amount of melanin production through tanning, the person cannot change from one skin type to another.

Ultraviolet rays are similar to other forms of radiant energy— including X-rays,white (visible) light and infrared—and all share similar properties. They are all electromagnetic waves that have the same form and travel at the same speed—86,000 miles per second—but differ in wavelength.Wavelength is the distance between the top of one wave to the top of the next. The longer the wavelength, the less aggressive the form of energy (not necessarily less penetrating); conversely, the shorter the wavelength, the more aggressive the form of energy.

Ultraviolet light is located between X-ray and visible light on the electromagnetic spectrum. UV has a higher frequency and shorter wavelength than visible light, and it has a lower frequency and longer wavelength than X-ray. UV, with its longer wavelength and less energy, is less penetrating than X-ray. In fact, UV only penetrates to the top layer of the skin. This is why analogies correlating X-rays to indoor tanning don’t make any sense.

UV can be broken down into three categories—UVA, UVB and UVC. UVA is found in the region between 320 and 400 nanometers. It has the longest wavelength and is the least powerful wavelength of the three, but this does not mean it is the least penetrating. UVA is the primary melanin oxidizer (darkener).

UVB is found in the region between 280 to 320 nm. It often is called the burning ray, because it is the wavelength primarily associated with erythema. But it is extremely important to note that a person can get burned by UVA, and contact with UVC could seriously burn an individual within a matter of seconds. UVB is the primary melanin stimulator and is necessary for the production of vitamin D in the skin.

UVC is found in the region between 200 to 280 nm and it often is referred to as the germicidal UV for its effectiveness in killing single-celled organisms. It is used in hospitals and water treatment plants for this purpose. Contact with UVC is extremely dangerous.

Even short overexposure can cause damage to the eyes and severe sunburn. It is emitted by the sun, but is absorbed almost entirely by the atmosphere. UVC is emitted by High Intensity Discharge (HID) lamps; therefore, these lamps require special filter glass to contain the output of the UVC spectrum.

When exposed to ultraviolet radiation, the melanocytes release extra melanin. This makes the skin darker and completes melanogenesis, which is defined as the UVR-induced production and oxidation of melanin, i.e., the process of developing facultative pigmentation, better known as cosmetic tanning. Facultative pigmentation is simply the level of an acquired tan developed by an individual exposed to ultraviolet light. Constitutive pigmentation is the skin’s natural color.

Both UVA and UVB play a role in the tanning process. The main role of UVA in the tanning process is to oxidize (darken) existing melanin. UVB is the primary melanocyte stimulator. The melanocytes then produce melanin.

The tanning process, or increased pigmentation, occurs in two phases. The first phase is immediate pigment darkening (IPD), which is a rapid darkening of already existing melanin. This begins during exposure to UV radiation and its maximum effect is visible immediately. IPD is most obvious in skin where significant pigmentation already exists, and is induced mainly by UVA. IPD may fade within minutes or may last several days and blend in with delayed tanning. Factors including skin type and previous exposure affect the response.

The second phase is delayed tanning, which is induced mostly by UVB exposure and is the result of increased epidermal melanin. It first becomes visible about 72 hours after exposure. Both UVA and UVB radiation start delayed tanning by creating an “excited” condition in the melanocytes, which in turn releases more melanin into the skin. The degree of IPD is primarily a reflection of the person’s skin type. Delayed tanning demands larger doses of both UVA and UVB for any given response.