I got swimmer’s itch from a poop-filled lake: summer rash explained

Picture this: It’s a blistering hot day and there’s a glistening body of water for you to cool down in. You swim, you have a good time, you feel refreshed you … break out in an unsightly and painful rash?

Enter swimmer’s itch, an allergic reaction that many people are unaware of, caused by a microscopic parasite that passes through feces and lives in some lakes, ponds and oceans.

Reagan Caussey went viral on TikTok after posting about her experience with the side effects, admitting she didn’t know about the condition before she got it.

“It’s so uncomfortable,” she captioned a TikTok video that has been viewed 6.5 million times.

In the video, Caussey shows her legs covered in tiny red bumps and some larger ones on her arms, adding she’s “lowkey scared to swim in lakes now.”

Caussey had been visiting her aunt in Texas when she went paddle boarding with some friends in Town Lake, responding to a comment on her TikTok saying she was “barely” in the water and showered after.

However, despite rinsing off in clean water, the 19-year-old woke up the next morning with her legs covered in a red rash, which later spread to the rest of her body.

The Dallas native told Buzzfeed News she thought it was an allergic reaction to her aunt’s cat, not realizing it was swimmer’s itch until her friends sent her a TikTok of another woman suffering from the same rash.

Tasha Marie Bell, who also shared her swimmer’s itch story on TikTok, said she initially thought she had bed bugs, later realizing that she only had the rash on the places the water had touched her.

“I did not know [swimmer’s itch] existed,” she said in the video viewed nearly 3 million times. “Just be careful about the water that you’re getting in.”

What is swimmer’s itch?

Swimmer’s itch, or cercarial dermatitis, is caused by an allergic reaction to a particular microscopic parasite, according to the Centers for Disease Control and Prevention, released into the water — both fresh and salt.

How a person becomes infected is complex, but it originates through the feces of infected animals ranging from “ducks, geese, gulls, swans and certain mammals such as muskrats and raccoons.”

Parasites produce eggs that pass through poop. If eggs land in the water, they hatch and release microscopic larvae, which then seek out certain species of aquatic snails to infect and multiply.

From there, snails release their own larvae, which can dig into the skin of swimmers, causing allergic reactions and rashes in humans.

The good news is the parasite’s preferred hosts are birds and mammals and will die shortly after burrowing into the skin of humans, although it will cause an itching and painful rash for a few days up to a week.

Swimmer’s itch is not contagious, but anyone who swims in infected water can get the ailment. Prevention includes avoiding marshy swimming areas and towel drying or showering immediately after leaving the water.

Most cases of swimmer’s itch do not require medical attention, but the CDC advises not to scratch.