A photosensitivity reaction is an abnormal skin response to sunlight, often caused by a medicine or a substance on the skin that reacts with ultraviolet light. Phototoxic reactions look like an exaggerated sunburn, while photoallergic reactions are itchy, eczema-like immune reactions.
Key symptoms
- Burning red skin after a short time in the sun
- Itchy eczema-like rash on sun-exposed areas
- Blisters in severe cases
- A new medicine before the rash, such as doxycycline, a thiazide or an NSAID
- Darker skin left behind after healing
What you find on exam
- Rash limited to the face, V of the neck, backs of the hands and forearms
- Shaded areas spared: under the chin, behind the ears, upper eyelids
- Sharp borders at clothing lines
- Streaks or odd shapes after contact with lime juice or plants (phytophotodermatitis)
Tests
- Detailed history of medicines, plants and skin products
- Photopatch testing for suspected photoallergy
- ANA and anti-Ro antibodies if lupus is possible
- Porphyrin levels if there are blisters and fragile skin on the hands
Treatment basics
- Stop or replace the trigger drug when possible
- Strict sun protection: shade, clothing and broad-spectrum sunscreen
- Cool compresses and topical steroids
- Oral antihistamines for itch; a short course of oral prednisone if severe
Red flags
- Widespread blisters or peeling skin
- Fever, joint pain or other organ symptoms (possible lupus)
- Blisters with mouth or eye sores after a new medicine (rule out Stevens-Johnson syndrome)
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Sources: NCCPA PANCE Content Blueprint; NBOME COMLEX-USA clinical presentations; AAMC Core Entrustable Professional Activities (Core EPAs). Written by Making Synapses. Making Synapses is not affiliated with these organizations.