Causes of Itchy Rashes After Ocean Swimming

Have you ever been enjoying a vacation at the ocean, swimming, surfing, or diving, and discovered you had an itchy rash? There are many causes of itchy rashes after swimming, including insect bites, cold urticaria, and sun allergy.

Woman sitting on the beach
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Microscopic organisms also cause special types of itchy rashes after swimming. This can occur either in salt water (the ocean) or fresh water (lakes, ponds, rivers, and streams).

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, can get trapped between a person's skin and bathing suit, wet suit, surfboard, or another object, causing an itchy, burning 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. Taking off the contaminated swimwear and washing may prevent additional rash and symptoms from developing.

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. It has been reported on beaches from New York to Florida, and it also occurs in the Caribbean.

The skin rash may last for many days, especially if the contaminated bathing suit is worn again without washing. Treatment includes the use of topical corticosteroid creamsoral antihistamines, and, occasionally, oral or injected corticosteroids.

Swimmer's Itch

Swimmer's itch, also known as cercarial dermatitis, occurs when people swim in water contaminated with parasites called schistosomes. It often occurs in fresh water, but it can also occur in marine habitats. Generally, swimmer's itch occurs 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. Not all species of schistosomes are the same: some cause more dangerous diseases in other parts of the world.

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 in shallow lakes where aquatic birds or freshwater snails are known to exist.

Swimmer's itch can occur in waters throughout the United States. There isn't a way to prevent getting swimmer's itch other than avoiding contact with contaminated lakes and rivers. Hot temperatures increase the risk of getting the infection.

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. Swimmer's itch isn’t contagious from person to person.

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.

Diving Suit Dermatitis

If you wear a scuba diving suit, you may end up with a bumpy red rash caused by a common bacterium, Pseudomonas aeruginosa. The bacteria can grow in a neoprene diving suit.

It can be prevented by proper care by cleaning your diving suit after every use with 0.45% lactic acid and taking a shower immediately after wearing your diving suit. If you suspect an infection, you should seek medical evaluation to determine whether you need to be treated with antibiotics. Patients with cystic fibrosis or other types of immunodeficiency may get particularly sick from infection with this bacteria.

Bikini Bottom Folliculitis 

Wearing wet bathing suit bottoms for long periods can result in deep bacterial folliculitis infections with Streptococcus, Staphylococcus aureus, or Pseudomonas aeruginosa. This can be prevented by changing out of wet swimwear promptly and showering immediately.

Bikini bottom infection is treated with oral antibiotics.

Folliculitis can also occur with diving suits and this is another reason to clean them with 0.45% lactic acid.

5 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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  3. 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. doi:10.1017/S0022149X09308020

  4. Tracz ES, Al-jubury A, Buchmann K, Bygum A. Outbreak of swimmer's itch in Denmark. Acta Derm Venereol. 2019;99(12):1116-20. doi:10.2340/00015555-3309

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By Daniel More, MD
Daniel More, MD, is a board-certified allergist and clinical immunologist. He is an assistant clinical professor at the University of California, San Francisco School of Medicine and currently practices at Central Coast Allergy and Asthma in Salinas, California.