Swimmer’s itch (cercarial dermatitis)
Swimmer’s itch is an allergic itchy skin rash caused by contact with flatworm larvae that live in fresh or saltwater lakes, ponds or lagoons. It is most common in areas with vegetation or where large numbers of birds gather and are frequently fed such as warmer, shallow water and around boat ramps.
Symptoms of swimmer’s itch
Red spots or blisters (ranging from small looking bites to larger welts) will appear on the body within hours of exposure. They can continue to grow in size after they appear. These spots can become itchy and usually last up to a week.
Some people can have a more severe ‘allergic response’ than others and others may not react at all. The rash is not contagious.
If you experience symptoms:
- wash or shower with clean water and dry yourself off with a towel
- avoid scratching the spots
- If your rash is itchy and uncomfortable, visit a pharmacy or healthcare provider for support - swimmers itch usually resolves within 1 to 3 weeks with treatment.
Repeat exposures can result in severe reactions. If the symptoms are severe, contact your usual healthcare provider or call Healthline free, 24 hours a day, 7 days a week on 0800 611 116
Diagnosing swimmer’s itch
If you think you or your child has swimmer’s itch and the rash is not improving or is getting worse visit a pharmacy or healthcare provider. You can also call Healthline free, 24 hours a day, 7 days a week on 0800 611 116
Treating swimmer’s itch
To help reduce irritation, pharmacies or your healthcare provider can provide treatment options.
Preventing swimmer’s itch
To reduce the risk of swimmer’s itch:
- avoid swimming in the morning and in shallow warm water where there are lots of birds or vegetation present
- wear swimwear that covers the skin and shower or towel dry after swimming
- avoid feeding or encouraging birds such as ducks, geese or swans near swimming areas or boat ramps.
Other names for swimmer's itch
Many countries have their own local names for swimmer’s itch including:
- duck itch (New Zealand)
- duckworms or duck fleas (US)
- hoi con (Thailand)
- kobanyo or kubure (Japan)
- sawah (Malaysia)
- rice paddy itch or clam diggers itch.