Chapter 4
The Tanning Process

� Melanocytes
� Tyrosine
� Melanin
� Immediate pigment darkening
� Delayed tanning

It is essential that you and your employees understand the biological process by which the skin tans when exposed to ultraviolet radiation. An understanding of the tanning process will aid you in educating your clients in the proper way of achieving the best tan possible.

Skin Absorption
Human skin is composed almost entirely of water and organic molecules. Molecules of organic compounds consist of nuclei which are in relatively fixed positions and electrons which are found in defined volumes surrounding the molecular structure. For each compound, certain electronic states exist, each of which corresponds to the distribution of electrons around the nuclei and a specific energy. At room temperature, all molecules are in the electronic state with the lowest energy, called ground state.

UV radiation must first be absorbed by molecules to cause any chemical change. Only that radiation absorbed by the skin can initiate a biologic response. A molecule that absorbs light is called a chromophore. These include molecules such as DNA, RNA, and proteins. After absorbing the energy of the radiation, the molecule is in an excited state. The molecule exists in this excited state for a fraction of a second before losing the energy at which time a chemical change occurs. The observable effect may be increased pigmentation of the skin or erythema.

The Tanning Process
To understand the tanning process one first needs to realize that the skin is comprised of several different types of cells. Each type of cell has a specific function. The cells involved primarily in the tanning process are called melanocytes. Melanocytes are located at the base of the epidermis between the epidermis and the dermis below. Melanocytes use the amino acid tyrosine to produce melanin. This melanin leaves the melanocytes and travels up through the epidermis where it reacts with the UVA and UVB radiation through a chemical reaction darkening the pigmentation of the skin. As we already know the skin consists of three layers of tissue: The epidermis or outer layer, the dermis or inner layer and the subcutaneous layer.

The tanning process or increased pigmentation occurs in two phases. The first one is immediate pigment darkening (IPD). IPD is a rapid darkening of the skin which begins during exposure to UV radiation and its maximum effect is visible immediately. It is caused by a change in melanin already present in the skin. IPD is most obvious in skin where significant pigmentation already exists. It occurs after exposure to the longer wavelength of UVA or visible light. IPD may fade within minutes of small exposures or may last several days after longer exposures and blend in with delayed tanning.

Delayed tanning, induced mostly by UVB exposure, is the result of increased epidermal melanin and first becomes visible 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.