top of page

Swimmer's Itch

Swimmers Itch LifeCycle.jpg

What is it?

Swimmer's itch, also called cercarial dermatitis, appears as a skin rash caused by an allergic reaction to certain microscopic parasites that infect some birds and mammals. These parasites are released from infected snails into fresh and salt water (such as lakes, ponds, and oceans).

How long does it last?

The rash, cercarial dermatitis, can last between 2-7 days. It appear as red blotches/spots on the skin, they are often itchy and can be a little painful.

How to treat?

More often than not it doesn't require treatment to clear up, however, if you wish to it is suggested that antihistamines, anti itch creams, calamine lotion or bathing in epsom salts can help. 

Why is it in our lake?

The parasite is spread by ducks... the eggs are then passed into any water the ducks visit when they defecate. The parasite eggs then hatch into the water and usually attach to snails and other molluscs. These then grow and leave the snail to find a new body to breed into. 

When the level of the water drops at Maidenhead the weed tends to grow faster bringing the gap between the top of the water to the weed level ever closer. Sailors rarely get affected as they sail in deeper water, Paddlers who fall in can be affected but tend to get back on their boards quickly. It mainly affects those who are continually entering the water in shallower water where there is a concentration of weed. 

Why doesn't everyone suffer?

This is where it seems there is little logic, it seems that some people are more susceptible than others to getting affected. A little like mosquitoes who seem to go after certain people. 


If you or anyone in your party chooses to enter the lake then avoid weedy areas. When the wind is from the north you do need to be aware that floating weed can congregate in the launching areas. It is highly likely this will mean that there will be a higher concentration of weed in these areas. 

We wish to advise you of the following:
1. Participants likely to enter the water should wear clothing which is close fitting at the wrists, neck and ankles, such as a wetsuit, along with boots over the clothing/wetsuit to minimise skin exposure.

2. Minimal time should be spent in shallow water particularly if weed is present where snails harbouring these pests live.

3. After coming ashore participants should hose themselves down or shower immediately with soap and warm water to wash off any of these parasites.
4. Be aware that if anyone is targeted by these parasites that the resulting dermatitis is likely to remain for 4-5 days or more. 

More information...

In the USA the CDC publishes a lot more information than we tend to get in the UK. Some of the advice here can be written. 

- Apply waterproof sunscreen before entering the water

- Towel off immediately after leaving the water

- Wash with soap and water in a hot/warm shower as soon as possible. 


Here's a link to what you might see if you get Swimmer's Itch...

bottom of page