Lakes Are Home to 'Itchy' Parasite.

• Position: WATERBORN RASH

A waterborne parasite with a forked tail is getting under our skin. Hot summer temperatures have warmed up lakes and watering holes, making conditions ripe for swimmer's itch, medically known as cercarial dermatitis.

The ailment widely is reported around the Pacific Northwest each summer, especially during extended periods of warm weather when the parasites flourish and more people are recreating in water, notes pediatrician Jennifer Troiano, clinical assistant professor at Washington State University's College of Medicine, Pullman.

Though generally harmless, the red pimply rash is maddeningly itchy. Caused by tiny wormlike parasites called schistosomes, "they penetrate the skin and trigger an immune response in the form of red spots that can persistently itch."

Schistosomes live their life cycles migrating from small snails to ducks and geese--and then back again, but they unintentionally can encounter humans along the way. Oftentimes, there are children playing in shallow water where the organisms tend to congregate, explains Troiano, adding that kids are less likely than adults to towel dry after coming to shore, also making them more susceptible.

"Drying off with a towel immediately after leaving the water and, if possible, rinsing off in a shower...