Itchy Rash After Swimming in the Ocean

Causes of an Itchy Rash After Swimming in Lakes or the Ocean

Swimmer's Itch is caused by parasites found in contaminated water. The parasite enters through the skin and a rash appears at the site of entry. © ADAM

Summer vacation brings to mind all sorts of great outdoor activities – from camping at the lake or trips to the beach, the warm summer months lead to water activities, such as swimming in the lake, surfing in the ocean or waterskiing in the river. Unfortunately, many people will experience an itchy skin rash after aquatic sports.

Many years ago, while I was living in Texas, I went "tubing" down the Guadalupe River.

The next day, I had an itchy rash all over my body that lasted for many days. My only relief came from the use of over-the-counter hydrocortisone cream applied daily for about a week.

There are many causes of itchy rashes after swimming, including insect bites, cold urticaria and many causes of sun allergy after a day in the sun. Microscopic organisms cause two special types of itchy rashes after swimming, one from exposure to freshwater (lakes, ponds, rivers, and streams), the other from salt water (the ocean).

Swimmer's Itch

Swimmer's Itch, also known as cercarial dermatitis, occurs when people swim in water contaminated with parasites called schistosomes. Generally, Swimmer's Itch occurs in freshwater, where aquatic birds and snails are likely to live. These animals serve as the hosts for the life cycle of the schistosome, although the parasite will enter the human skin, causing an irritating or allergic rash as it dies.

In many parts of the world, schistosomes cause a variety of dangerous parasitic infections in humans, but not in the United States.

Cercarial dermatitis causes an itchy, bumpy, red rash on exposed skin not covered by a bathing suit. The rash usually develops within a day of exposure to contaminated water, especially shallow lakes where aquatic birds or freshwater snails are known to exist.

Swimmer's Itch is most common in the Mid-Western United States but also occurs in warmer climates such as Texas as New Mexico. There isn't a way to prevent getting Swimmer's Itch other than avoiding contact with contaminated lakes and rivers.

The rash from Swimmer's Itch usually goes away with a week, with or without treatment. The schistosome doesn’t cause a parasitic infection in humans – it dies in the skin but still causes a skin rash. The rash is best treated with topical corticosteroid creams and oral antihistamines, although occasionally needs medical attention and treatment with oral or injected corticosteroids and even antibiotics if a secondary bacterial infection is present. Swimmer's itch isn’t contagious from person to person.

Seabather's Eruption

Seabather's Eruption is an itchy rash that occurs after swimming in the ocean and being exposed to jellyfish-like larvae. These larvae, which are either very small or microscopic, get trapped between a person's skin and bathing suit, wetsuit, surfboard or another object, causing an itchy, burning skin rash on areas covered by clothing. Symptoms often start while the person is still in the ocean, but may occur many hours after exposure.

Rubbing the skin makes the symptoms worse, as the larvae release a toxin into the skin as a result of pressure or friction. Occasionally, in addition to the itchy skin rash, a person may experience systemic symptoms from the toxin, such as fever, chills, nausea, vomiting, headache and diarrhea.

Seabather's Eruption most commonly occurs along the East Coast of the United States and has been reported from New York to Florida. The skin rash may last for many days, especially if the contaminated bathing suit is worn again without washing. Treatment is similar to that of Swimmer's Itch and includes the use of topical steroid creams, oral antihistamines and the occasional need for oral or injected corticosteroids.


Brant SV, Loker ES. Schistosomes in the Southwest United States and Their Potential for Causing Cercarial Dermatitis or “Swimmers Itch”. J Helminthol. 2009;83:191-98.

Verbrugge LM, Rainey JJ, Reimink RL, Blankespoor HD. Swimmer’s Itch: Incidence and Risk Factors. Am J Public Health. 2004;94:738-41.

Rossetto AL, Dellatorre G, Silveira FL. Seabather’s Eruption: A Clinical and Epidemiological Study of 38 Cases in Santa Catarina State, Brazil. Rev Inst Med Trop San Paulo. 2009;51:169-75.

Zoltan TB, Taylor KS, Achar SA. Health Issues for Surfers. Am Fam Physician. 2005;71:2313-20.

Freudenthal AR, Joseph PR. Seabather’s Eruption. NEJM. 1993;329:542-4.

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