People who bathe in fresh water, inhabited by water snails can get intense itching, blisters, red bumps and such from cercariae. These are tadpole-like small animals – a kind of flukes or flatworms – which are less than 1 mm in length. Part of their life cycle takes place in certain freshwater snails.

This stage, the cercaria, which in large swarms leaves the snails, drills into the skin of a bird or – a human – shortly hereafter. The cercariae that end up in human skin, die no later than one day after, but the itching and skin symptoms can last for days and weeks.

Cercarial skin symptoms may be quite common. They can be easily confused with other types of rashes and itching from insect and plants and are therefore rarely detected. If you have itching and rashes after bathing or dabbling in a lake or a pond, cercariae should be considered as a possibility.