The exact cause of solar urticaria is unknown, but we do know that it occurs when sunlight activates the release of histamine or a similar chemical in skin cells. This mechanism is described as an antigen-antibody reaction and urticaria is the resulting inflammatory response.
Solar urticaria can also stem from:
- dermatitis;
- genetic inheritance;
- use of antibiotics or other medications;
- regular use of perfumes, disinfectants, dyes or other chemicals that can trigger the symptoms of this condition, when an individual is exposed to sunlight.
Areas of the skin that are rarely exposed to the sun are more likely to be affected. Skin reactions usually appear within minutes of exposure. The appearance of the rash may vary depending on the person's sensitivity. Hives may sometimes blister or crust , but they won't scar.
Although 35 is the median age for a first sun-induced hive attack, no one is immune!