Photoallergic dermatitis
| Classification according to ICD-10 | |
|---|---|
| L56.2 | Photoallergic reaction to drugs |
| ICD-10 online (WHO version 2019) | |
A photoallergic dermatitis is a skin disease , first a specific in the sensitization of the skin by different substances occurs. If sunlight subsequently hits the skin, it leads to reddening of the skin, nodules and occasionally blistering. Photoallergizing substances can lead to sensitization both locally through contact with the skin from outside ( photoallergic contact dermatitis ) and systemically through absorption via the gastrointestinal tract ( systemic photoallergic dermatitis ). The treatment of acute symptoms is the same as for other allergic eczema . In addition to avoiding sensitizing substances, long-term therapy includes suitable sun protection .
causes
Important locally sensitizing photoallergens are halogenated salicylanilides, fenticlor, hexachlorophene , bithionol and rarely also light protection filters. Examples of triggers for systemic photoallergic dermatitis are the ingestion of phenothiazines , sulfonamides , hydrochlorothiazide or quinidine derivatives . Only in connection with exposure to UV-A light does a reaction of the immune system that is comparable to other allergic reactions occur. In contrast, phototoxic reactions occur without mediation by the immune system.
clinic
Restricted to the exposed skin areas and, in the case of photoallergic contact dermatitis, to the areas that were in contact with the sensitizing substances, skin reddening ( erythema ), nodules ( papules ) and small vesicles ( vesicles ), more rarely blisters ( bullae ), appear. Continued allergen intake results in chronic photoallergic eczema with slight reddening , but extensive thickening with coarse skin lines ( lichenification ) and scaling , limited to exposed skin areas. Scattered foci lead to a blurred boundary. There is always a distinct itchiness .
Diagnosis
As a rule, the diagnosis arises from the collection of the medical history and the clinical examination. If this does not yet result in a clear diagnosis, a photo patch test can be carried out in the case of photoallergic contact dermatitis, in particular to determine a clear triggering substance. This can fail in systemic photoallergic dermatitis , especially if a metabolic product of the substance originally ingested is the relevant photoallergen. In such cases, systemic photo provocation can be performed.
Photo patch test
The suspected triggers are applied to test patches and stuck to the back on both sides. After 24 hours, one side is removed and irradiated with UV light. After 48 hours, the second side is also removed. The skin areas are marked and examined for abnormalities such as redness, blisters, etc. Another reading is taken after 72 hours.
Photo provocation
For a photo provocation, a skin area is first exposed. The suspicious substance is then administered and a second skin area is irradiated with UVA at the time of the highest blood plasma concentration . The reading takes place after 24 and 48 hours.
therapy
Treatment should, if possible, consist of eliminating the photoallergen. Acute and chronic skin changes are treated like other eczema of an allergic origin. Dense clothing and sunscreen with UVA filters can provide suitable light protection.
See also
Individual evidence
- ↑ a b c d e f g P. Lehmann, T. Schwarz: Photodermatoses: Diagnostics and therapy. In: Deutsches Ärzteblatt Int. 2011; 108 (9), pp. 135-141. Retrieved September 13, 2013.
- ↑ Peter H. Höger: Pediatric Dermatology. Schattauer, Stuttgart 2011, ISBN 978-3-7945-2730-4 .
- ↑ AWMF recommendation (expired) for carrying out the photopatch test and other test procedures for the identification of photosensitizers (.pdf), section 3. Indications
- ↑ Photo patch test - indication, implementation, procedure , University Hospital Marburg, accessed on March 4, 2018.
