After exposure to water affected by the schistosomes, a prickling or itchy feeling begins that can last up to an hour while the flukes enter the skin. Small red macules form, but there may be swelling or wheals among sensitive children. As these lesions begin to disappear, they are replaced after 10 or 15 hours by discrete, very itchy papules surrounded by a red area. Vesicles and pustules form one or two days later; the lesions fade away within a week, leaving small pigmented spots. Different symptoms depend on how sensitive the patient is to the schistosome; each reexposure causes a more severe reaction.
The best way to alleviate the problem is to destroy the snails by treating the water with copper sulfate and carbonate, or with sodium pentachlorophenate. A thick coating of grease or tightly woven clothes can protect against infestation; bathing with a hexachlorophene soap before swimming may help to some degree. Briskly rubbing the skin with a towel after swimming may help remove some organisms.
Calamine lotion or oral antihistamines may help control the itch until the lesions begin to disappear on their own.