Occupational carprofen photoallergic contact dermatitis

The nonsteroidal anti-inflammatory drug carprofen was used in humans in the 1980s, before its withdrawal due to adverse effects. It re-emerged for veterinary uses, for which it is still widely prescribed, in the 1990s. There has been one previous report published of photoallergic contact dermatitis (PACD) in a pharmaceutical factory worker exposed to carprofen.

Investigation of carprofen as a cause of PACD in pharmaceutical factory workers presenting with facial dermatitis.

Photopatch testing to carprofen dilutions in two pharmaceutical factory workers and three healthy volunteer controls using the European consensus methodology. This was followed by testing of eight further employees, referred by occupational health services, in the same factory.

The index patient suspected a problem with carprofen and was found to have PACD to carprofen. The second patient presented with a widespread, although especially photoexposed site, dermatitis and was initially labelled as having an 'unclassified dermatitis'. Only subsequently was her exposure (indirect; she did not work in the packaging section of the factory like the first patient) to carprofen recognized and testing confirmed both contact allergy and PACD to carprofen. One of three healthy volunteer controls had an active photoallergy sensitization event to carprofen starting 10 days after photopatch testing. Three of eight factory employees subsequently referred because of skin problems had carprofen PACD.

Carprofen is a potent photoallergen. These cases emphasize the importance of photopatch testing, and considering agents not included in standard series, when investigating patients presenting with a photoexposed site dermatitis.