Don't let swimmer's itch ruin your time at the lake. Know before you go — get real-time swimmer's itch updates from lakes across the US and Canada, submitted by swimmers like you.
From understanding the science to protecting yourself and finding relief — grounded in peer-reviewed research.
Learn the science behind cercarial dermatitis — the parasite lifecycle, the species differences, and why some lakes are far worse than others.
Learn More →From individual protection strategies to large-scale lake management programs proven to dramatically reduce swimmer's itch outbreaks.
See Strategies →Already affected? Discover what actually works to stop the itch, reduce inflammation, and speed your skin's recovery after exposure.
Find Relief →Help your community stay informed. Report swimmer's itch at your lake and browse the real-time map to see where outbreaks are active.
Report Now →Swimmer's itch (cercarial dermatitis) is a skin rash triggered by an allergic reaction to microscopic parasites — schistosome cercariae — that normally infect aquatic birds and mammals. When an infected snail releases thousands of these larvae into the water, they can mistake a swimmer for their intended bird or mammal host.
Once the cercariae contact human skin, they attempt to burrow in. The human immune system attacks them, and it's this allergic reaction — not the parasite itself — that causes the characteristic red, itchy bumps.
Not all swimmer's itch is created equal. There are 16 varieties of freshwater swimmer's itch depending on the species of waterfowl and snails present. Some varieties, such as those produced by Canada Geese, will only produce mild irritation in humans. Whereas swimmer's itch derived from Common Merganser ducks has been proven to be 45× more severe to humans than other forms of swimmer's itch.
Learn the Full Science →Eggs shed by infected ducks are picked up by snails, which release cercariae that can penetrate human skin.
Swimmer's itch is manageable when you know the right strategies. Individual precautions can significantly reduce your risk. Practice some of these strategies to help mitigate your exposure.
Snails concentrate in rocky or sandy shallows under 3 ft. Deeper water carries significantly lower risk.
A thick barrier of zinc-based sunscreen followed by petroleum jelly creates a physical shield against cercariae penetrating your skin.
For common varieties, vigorous toweling before the water evaporates removes cercariae before they can burrow. Less effective against the Merganser variety.
Relocating Merganser broods within 24 days of hatching eliminates the primary parasite source. Michigan's Higgins Lake achieved a 98% reduction in cases utilizing this approach.
Kills snails in treated areas but provides only localized, temporary relief — wind and currents continue to spread cercariae. Permitted in many states but can have adverse effects on lake ecology and non-target species.
Swimmer's itch reactions typically resolve within 5–7 days, but the right approach can dramatically reduce discomfort. The key is acting quickly — the sooner you treat, the milder the reaction.
Apply immediately to reduce inflammation and numb the itch. Most effective in the first 24 hours after exposure.
Hydrocortisone cream (1%) reduces inflammation. Calamine lotion provides soothing relief for mild-to-moderate cases.
Benadryl or cetirizine reduce the allergic response significantly and help with sleep when itching is severe.
Shower with soap as soon as possible after swimming. Removes cercariae still on the surface before they fully penetrate.
Initial reaction as cercariae attempt to burrow. Apply a cold compress immediately.
Raised, itchy bumps appear. Begin antihistamines and topical cream now.
Itching is most severe. Avoid scratching — it worsens inflammation and risks infection.
Bumps begin to flatten. Continue antihistamines. Keep skin moisturized.
Most cases resolve fully. See a doctor if symptoms worsen or show signs of infection.
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