[Phototoxic and photoallergic reactions].
1Universitätshautklinik der Heinrich-Heine-Universität Düsseldorf, Moorenstr. 5, 40225 Düsseldorf, Germany. neumannt@uni-duesseldorf.de
Summary
Photosensitizers can cause skin reactions after UV exposure. The photopatch test is a reliable method for identifying these substances, with other tests available if needed.
Area of Science:
- Dermatology
- Toxicology
- Photobiology
Context:
- Photosensitizers, both natural and artificial, can induce skin sensitivity upon ultraviolet (UV) exposure.
- UV exposure can lead to phototoxic or photoallergic reactions, necessitating accurate identification of causative agents.
Purpose:
- To differentiate between phototoxic and photoallergic dermatitis based on clinical observations and studies.
- To introduce and evaluate the photopatch test as a diagnostic tool for photosensitizer identification.
- To outline alternative testing methods when the photopatch test is inconclusive.
Summary:
- The photopatch test, an illuminated version of conventional epicutaneous tests, serves as a screening method for photosensitizers.
- Its diagnostic accuracy in specificity and sensitivity is comparable to standard epicutaneous testing.
- Additional tests like photoprick, photoscratch, and illuminated intracutaneous tests are available for cases where the photopatch test yields no relevant reactions.
- Systemic photoprovocation tests are indicated when the photosensitizer is a metabolite of the tested substance.
Impact:
- Provides clinicians with a validated method for diagnosing photosensitivity reactions.
- Improves the differential diagnosis between phototoxic and photoallergic dermatitis.
- Offers a tiered approach to identifying photosensitizers, enhancing diagnostic yield.
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