Suntanning is very dangerous because it causes skin discoloration and other body complications such as cancer as a result of the exposure to the dangerous UV rays. The body requires exposure to these rays to stimulate the production of vitamin D, but very little sunlight is required for this purpose.
Tanning shows as a sign of skin damage and is what the body uses to try and protect the skin from ultraviolet rays. The pigment responsible for tanning is melanin, which is found in the skin, eyes and hair, and it is produced by melanocyte cells located in the epidermis. During exposure to the sun, melanin is produced by the skin to absorb UV rays. The more the rays hit the skin, the more the pigment is produced. This is what causes skin to darken in sunlight.
If only a small amount of melanin is produced, UV rays can permanently damage the skin. Sunlight normally affects the DNA of the skin cells as a result of the little production of melanin. If the damage accumulates over time, mutation of cells can occur, potentially leading to skin cancer. Persistent damage from UV rays also causes skin discoloration and sagging.