Fotoallergie

Fotoallergie, also known as solar urticaria, is a rare condition characterized by hives or a rash that appears on skin exposed to sunlight. This reaction is typically immediate, developing within minutes of sun exposure, and can cause itching, redness, and swelling. The affected areas may also feel warm to the touch. The severity of the rash can vary from mild irritation to severe blistering in some cases.

The exact cause of fotoallergie is not fully understood, but it is believed to be an immune system response to sunlight. Certain wavelengths of ultraviolet (UV) radiation, primarily UVB and sometimes UVA, are thought to trigger a reaction in the skin. This reaction may involve the release of histamine and other chemicals that cause the characteristic symptoms of urticaria. In some individuals, specific medications or chemicals applied to the skin may also contribute to photosensitivity, leading to a photoallergic reaction.

Diagnosis of fotoallergie is usually made based on a patient's history and a physical examination. Phototesting, where small areas of skin are exposed to controlled amounts of UV light, can help confirm the diagnosis and identify the specific wavelengths that trigger the reaction. Treatment primarily focuses on avoiding sun exposure. This can involve wearing protective clothing, using high SPF sunscreen, and staying indoors during peak sunlight hours. Antihistamines may be prescribed to alleviate itching and reduce the severity of hives. In more severe or persistent cases, other therapies like phototherapy with controlled doses of UV light or medications that suppress the immune system might be considered.