Photoallergic reactions to olaquindox in swine raisers: role of growth promoters used in feed.

Background. The diagnosis of photodermatosis is generally facilitated by th e typical localization of the eruption. The causal agent can usually be ide ntified by history taking, allowing eviction and cure. it may be difficult to find the causal agent in cases with a sequential course. The occupationa l and/or recreational environment may provide helpful information. We prese nt two cases of photodermatosis related to the occupational environment. Case reports. A 50-year-old woman and a 29-year-old man were farm workers, both consulted for photoinduced eczema. The eczema was triggered by episodi c manipulation of an antibiotic used widely for preparing animal feed. The standard allergy tests were negative. The photobiology exploration led to t he diagnosis of photoallergy to olaquindox, a growth promotor added to anim al feed. The course was favorable after eviction or protection against the product, providing a complementary proof of its triggering effect. Discussion. We emphasize the contribution of photobiological explorations i n difficult cases with an occupational background. Generally, these patient s are unaware of the composition of the products manipulated, such as feed additives.