Swimmer’s Itch, also known as Cercarial Dermatitis, is an itchy skin rash caused by an allergic reaction to certain parasites that infect birds and mammals. The parasites’ larvae, known as cercariae, can penetrate human skin while swimming in contaminated water, causing red, raised, and itchy spots. The condition is generally harmless and resolves on its own, but antihistamines and topical treatments can alleviate symptoms.