Invisible rays that are part of the energy that comes from the sun. Ultraviolet A radiation also comes from sun lamps and tanning beds. Ultraviolet A radiation may cause premature aging of the skin and skin cancer. It may also cause problems with the eyes and the immune system. Skin specialists recommend that people use sunscreens that protect the skin from ultraviolet radiation. In medicine, ultraviolet A radiation also comes from special lamps or a laser and is used to treat certain skin conditions such as psoriasis, vitiligo, and skin tumors of cutaneous T-cell lymphoma. Also called UVA radiation.