Swimmer’s Itch

What is Swimmer’s Itch?

Cercarial dermatitis is another name for swimmer’s itch and it is caused by an allergic reaction to a parasite that lives in bodies of water. A mature form of the parasite is found in the blood of various fowl including geese and ducks, and some small mammals. The eggs of these parasites enter bodies of water through the feces of the fowl and mammals.

After hatching, the larvae infect and multiply inside a certain type of snail. When the larvae leave the snail, it looks for a mammal or bird as a host and the cycle begins again. If an individual is in the water while the larvae are searching for a host, the larvae will bore through the skin of the individual, which causes the allergic reaction.

What are the Symptoms of Swimmer’s Itch?

People who have swimmer’s itch will feel an itching, burning or stinging sensation on their skin. This type of allergic reaction causes a red rash that contains pimples, which will eventually turn into blisters.

The burning or itching may start in a few minutes after the individual becomes infected or it may take several days for these symptoms to develop. It takes less than twelve hours for the pimples to begin appearing on the skin. Individuals should not scratch the rash as this can cause a consequential infection.

Swimmer’s Itch Causes

Swimmer’s itch is caused by a microscopic parasite that usually infects birds and mammals. It is typically found in fresh and salt water when infected snails contaminate the water. When it comes into contact with humans, the parasite burrows into the skin and causes an allergic reaction.

Swimmer’s itch cannot be passed directly from one person to the next – it only occurs after an individual has come into contact with contaminated water. People who swim or wade in ponds, lakes or the ocean are therefore at risk of developing the condition.

Shallow waters tend to be affected most. The water becomes contaminated when aquatic snails are infected themselves with the parasite, when it is in a larvae stage and still able to swim.

Prior to becoming larvae, the parasite would have originally come from infected birds and mammals which pass feces containing the parasite’s eggs. If the feces enters water, the eggs can hatch into larvae which then infects the snail and develops into more advanced larvae.

It is this form of the larvae which is then released from the snail and enters the water to search for a host to produce eggs in. Although in humans the larvae cannot survive or reproduce, they will still cause a temporary allergic reaction.

How is Swimmer’s Itch Treated?

The itchy rash will normally go away by itself in a week or so and medical treatment is usually not necessary. Individuals can help relieve their symptoms by placing cool cloths on their skin to ease the itching and burning. Anti-itching creams and calamine lotion can also be applied to the rash. If the rash fails to get better after a week or if there are red streaks on the skin or the presence of pus, individuals should contact a medical professional as soon as possible.

Swimmer’s Itch Prevention

There are a few tactics people can adopt to reduce the risk of getting Swimmer’s Itch. Firstly, they should avoid exposure by swimming in areas which are well-known for the problem. They should also avoid wading or swimming in particularly marshy waters, since this is where aquatic snails are often found. If a pier or dock is available for accessing the water, use it, as this might help to avoid the parasites which are most commonly found in shallow areas.

Secondly, after swimming in a lake, pond or ocean, it’s important to clean the skin as soon as possible. This may help to remove the parasite from the skin before it burrows. It may also help to apply a waterproof sunscreen to the skin before wading or swimming, as this could act as a barrier to the parasites.

Finally, it’s important to avoid attracting birds to any areas where swimming is common. This is because birds are responsible for initially introducing the parasite into the water via their feces. Do not throw food for birds, and dispose of any leftover food far away from the water.

Last Reviewed:
October 09, 2016
Last Updated:
November 30, 2017