Is it possible to have a sun allergy? If my skin is exposed to the sun even for a few minutes, I break out in hives.

Answers from James T C Li, M.D., Ph.D.

Yes, it's possible to have a sun allergy — though this is very rare. In sensitive people, direct sun exposure can trigger an immune system response that activates inflammatory cells or proteins in the skin. The result may be an itchy, red rash or hives (solar urticaria). This reaction usually fades within 24 hours after sun exposure.

More commonly, however, certain medications, chemicals or conditions cause increased sensitivity of the skin to sun exposure (photosensitivity). For example, you may experience a red rash on exposure to sunlight if an ingredient in your sunscreen or perfume causes photosensitivity. This reaction causes an increased sensitivity to sunlight, but is not technically an allergic reaction.

If you have sun allergy or an increased sensitivity to the sun, you can reduce your risk of a reaction by:

  • Limiting your time in the sun
  • Wearing sunglasses and protective clothing, such as long-sleeved shirts and wide-brimmed hats, when you're outside

If you have solar urticaria, your doctor may also recommend the use of antihistamines to prevent or reduce a reaction. Using sunscreen may offer some protection. Also, sunscreens don't block out ultraviolet rays completely, so you may still experience a skin reaction.

May 01, 2008