When the skin cells are exposed to large amounts of UV radiation, they undergo cellular death; as a result, your DNA is damaged. This causes sunburn, reduces the skin’s ability to repair itself, and unleashes tissue-damaging, inflammatory mediators from the immune system. This weakening of the skin’s mechanism is the main biological feature light-induced aging. In order to avoid premature aging, sagging skin, and wrinkles - and, more important, reduce your risk of skin cancer you need to protect your skin from the sun.
The more sun exposure, the more melanin the skin produces, which results in a suntan sign that the skin has already been damaged by ultraviolet (UV rays). If sun exposure continues, the UV rays will damage cells and blood vessels in the outer layer of skin, causing the redness and painful inflammation of sun¬burn, actually a minor burn.