Photodermatitis

A photoallergic dermatitis is a skin disease in which first enters a specific sensitization of the skin by different substances. Then When sunlight hits the skin, it causes skin redness, nodules, and occasionally blistering. Photoallergisierende substances locally through contact with the skin from the outside ( photoallergic contact dermatitis) and systemically via absorption through the gastrointestinal tract to cause sensitization (systemic photoallergic dermatitis). Treatment of acute symptoms is similar to that in other allergic eczema. For permanent therapy in addition to avoidance of sensitizing substances include a suitable sun protection.

Causes

Important local sensitizing photoallergens are halogenated salicylanilides, fenticlor, hexachlorophene, bithionol and rarely sunscreen. Examples of trigger a systemic allergic dermatitis photo are the absorption of phenothiazines, sulfonamides, hydrochlorothiazide or Chinidinderivaten. Only in conjunction with exposure to UVA light enters one other allergic reactions similar reaction of the immune system. In contrast, phototoxic reactions to occur without the mediation of the immune system.

Clinic

Limited to the exposed areas of the skin and photoallergic contact dermatitis on the places that were in contact with the sensitizing substances occur first skin redness ( erythema ), nodules ( papules ) and small vesicles ( vesicles ), rarely blisters ( bullae) on. With continued allergen supply a chronic photoallergic dermatitis with little redness, but areal thickening with coarsened skin lines ( lichenification ) and scaling arises limited to exposed areas of skin. Scattered foci result in an unclear boundary. Always there is a significant itching.

Diagnostics

Usually results in the diagnosis of the collection of medical history and clinical examination. This results in no clear diagnosis, photoallergic contact dermatitis, a photo patch test can be carried out in particular for determining which single -causing substance. This can fail in systemic photoallergic dermatitis, particularly when a metabolic product of the original substance is added the relevant photoallergen. In such cases, a systemic photoprovocation be performed.

Photo patch test

Here, the suspected triggers are applied to test patch and double-sided taped to the back. After 24 hours, one side is removed and irradiated with UV light. After 48 hours the second side is removed. The reading is taken after 72 hours.

Photoprovocation

For a photoprovocation first a skin area is exposed. Then the suspect substance is administered and the time of highest plasma concentration irradiated a second area of ​​skin with UVA. The reading is taken after 24 and 48 hours.

Therapy

Treatment should be as far as possible in eliminating photoallergen. Acute such as chronic skin lesions, like other allergic eczema cause treated. Waterproof Clothing and sunscreen with UVA filters provide appropriate sun protection.