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Cercarial dermatitis (swimmer's itch) is a cutaneous inflammatory response usually associated with penetration of the skin by cercariae of bird schistosomes.  Symptoms include reddening and itching of exposed skin in the water or immediately after emerging.  This is an indication of initial penetration of the cercariae.  After a period of approximately 12 hours, pruritic papules may become vesicular.  Scratching the affected areas may result in secondary bacterial infections.  An interesting note is that previous contact with cercariae can lead to a more immediate and intense immune response.  Proper identification of cercariae which may cause cercarial dermatitis is best left to investigators with a good background in trematode morphology as well as malacology.

A	B

A, B: Cercariae of Austrobilharzia variglandis, which can cause cercarial dermatitis.  Note the forked 'tail' and a pair of 'eye spots' near the anterior end (Figure B).