phytophotodermatitis

Last reviewed 01/2018

Phytophotodermatitis is a nonimmunologic, phototoxic response to the release of psoralens by plants. The psoralens are activated by light (long wavelength UVR) causing a streaky pigmented erythema, often, with blistering and hyperpigmentation (1).

Vesicular or bullous eruption occurs within 24-48 hours after exposure to the photosensitizing compound. The hyperpigmentation may persist for weeks or even months (2).

Exposure is usually through topical contact, but it may be through ingestion as well (3). The most common causes are umbelliferous plants such as cow parsley, giant hogweed, cow parsnip, and celery. Other recognized causes include exposure to the juice of Rutaceae (bergamot, orange, and lemon), Ranunculaceae, and Moraceae plant species (3).

Usually the arms and the legs are affected but the exact distribution will depend upon the circumstances in which contact was made.

Conservative treatment with oral and topical steroids is effective (4).

Click here for an example image of this condition

Reference:

• (1) Pomeranz MK, Karen JK. Images in clinical medicine. Phytophotodermatitis and limes. N Engl J Med. 2007;357(1):e1.
• (2) Birch K, Lovell C. Cutaneous reactions to plants. CPD Bulletin Immun Allergy 2004;3(3);77-81
• (3) Wynn P, Bell S. Phytophotodermatitis in grounds operatives. Occup Med (Lond). 2005 ;55(5):393-5.
• (4) Klaber RE. Phytophotodermatitis. Arch Dis Child. 2006;91(5):385