Cercarial dermatitis

If anaphylaxis occurs, treat immediately with adrenaline (epinephrine)—see advice on anaphylaxis.

Cercarial dermatitis (also known as swimmers’ itch) is an acute allergic dermatitis that develops after contact with schistosomes (Schistosoma species) when swimming in freshwater lakes. Schistosomes are parasites of birds, ducks or cattle, and use snails as their intermediate host. An initial pricking sensation (caused by the schistosome larvae penetrating the skin) is followed by an itchy macular rash. After 10 to 15 hours, an itchy papular and vesicular eruption appears on skin not covered by swimwear. The rash resolves spontaneously over a few weeks, but can leave pigmentation that takes months to resolve.

To treat cercarial dermatitis, use topical antipruritics and, if necessary, topical corticosteroids as for insect bites.