My old roommate loved to swim in a lake near our house. One day he said, “Well, I’m done swimming in the lake, it gave me swimmer’s itch.” He had a red bumpy rash on the skin where the water had lapped against his neck and shoulders. Not being a lake person, I never wanted to swim there. However, swimmer’s itch can occur from swimming in any body of fresh or salt water if it has become infected with the larvae from a certain breed of snail.
Swimmer's itch, also called cercarial dermatitis, is an allergic skin reaction that comes from swimming in contaminated water. Aquatic birds or mammals that live near the water can become infected with a parasite. The parasite lays eggs in the animal that end up in the animal’s feces, which hatch into larvae.
These larvae then infect a certain type of aquatic snail and are re-released as developed larvae (called cercariae) into the water. The larvae burrow into the skin of people swimming in lakes or the ocean causing a red papule-like itchy rash to develop. The larvae cannot survive long on human skin so they do die off but not without causing an allergic reaction first.
Symptoms of swimmer’s itch are: red pimples that occur 12 hours after swimming that may develop into blisters. Burning, tingling or itching may last up to a week after exposure then gradually diminish. However, the more often a person is exposed to the contaminated water, the more severe the symptoms may be. Excessive scratching may also cause a secondary skin infection.
Treatment for swimmer’s itch usually does not require a doctor’s visit. Topical soothing applications of calamine, baking soda pasta mixed with water or ice compresses may help. Baths in Epsom salt or oatmeal-based products like Aveno may relieve more severe itching. Over the counter steroid creams can be used.
Swimmer’s itch is not contagious so it cannot be spread from person to person. Additionally, once a swimming area has become contaminated with the larvae that causes swimmer's itch it does not mean that the area will always be unsafe.