The penetration causes a dermatitis which is usually accompanied with intense itching but, they do not mature into adults in the human body. Cases of cercarial dermatitis can occur in both fresh and brackish water environments. One species of schistosome often implicated in cases of cercarial dermatitis is Austrobilharzia variglandis , whose normal hosts are ducks. The snail, Nassarius obsoletus , is the intermediate host for this species and can be found at marine beaches in temperate climates. The areas of skin affected by seabather's eruption is generally under the garments worn by bathers and swimmers where the organisms are trapped after the person leaves the water.
Cercarial dermatitis occurs on the exposed skin outside of close-fitting garments.
Typically, hosts of avian schistosomes are migratory water birds, including shorebirds, ducks, and geese. Adult worms are found in the blood vessels and produce eggs that are swallowed and passed in the feces . On exposure to water, the eggs hatch and liberate a ciliated miracidium that infects a suitable molluscan intermediate host . The parasite develops in the intermediate host, usually a certain species of snail , to produce free-swimming cercariae that are released under appropriate conditions and penetrate the skin of the birds to complete the cycle . A number of species of dermatitis-producing cercariae have been described from both freshwater and saltwater environments, and exposure to either type of cercariae will sensitize persons to both.