Researchers want to help you scratch your itch to swim, without getting swimmer's itch

Researchers at the University of Alberta want to learn more about the parasite that causes swimmer's itch.

Swimmer's itch is caused by a flatworm parasite that penetrates the skin, said Patrick Hanington, associate professor in the school of public health at the University of Alberta.

The parasite uses freshwater snails as a host, he said.

"The parasite will die in your skin, which is what actually is happening when that red bump forms," Hanington told CBC Tuesday. "That itchy red bump is actually caused by your immune response killing the parasite in your skin."

The microscopic parasite leaves the snail by "coming right out of the body — a lot like that movie Aliens," Hanington said.

Hanington and his team have been studying swimmer's itch in Alberta since 2011.

They have a website swimmersitch.ca that provides information on their research, a survey for people to report contracting the rash, and a new map each summer showing lakes across Canada and into the United States where swimmer's itch has been reported.

Using past survey data from the website, they have concluded it could be a problem in any lake in the country.

Between 2013 and 2015 it was found in 101 lakes across Alberta.

Information from past surveys found that 10 to 15 per cent of those who get the rash go to see a physician, he said.

But just because a lake has swimmer's itch doesn't mean it should be avoided, he said.

"It's really about testing the water a little bit before you get in," he said.

Don't avoid lake swimming

At first, don't spend a long time in the water, get out after 10 minutes and check your skin for red spots. If a rash develops, Hanington said, stay out of the water, since it's likely you'll develop a worse case of swimmer's itch.

Some people have misconceptions about swimmer's itch.

Most of the other parasites penetrate your skin while you're still in the water, so there's no way to avoid contracting swimmer's itch, he said.

But you can minimize the chances of getting the rash.

Early July to mid-August are peak season for swimmer's itch. Avoid swimming in the early morning, since that's when the parasites tend to emerge from their snail hosts and are most active.

Hanington suggests staying away from reeds and plants in a lake because that's where snails are often found.

"We're trying to learn a little bit about the species of parasite that cause swimmer's itch here and what animals they're using as their hosts, which ultimately we hope will help us predict when and where swimmer's itch is most at risk to people who are using the lakes in Alberta," Hanington said.