3 Common Types of Ocean Rashes

An ocean rash is not uncommon after swimming, surfing, or diving in open water. Parasites that cause swimmer's itch are one of the most common reasons for this type of irritating rash. However, other insect bites as well as bacteria may also be to blame.

Itchy rashes that develop after swimming in the ocean are usually easily treatable and preventable.

This article explains why you might develop a rash after swimming in the ocean and what you can do about it.

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 salty ocean water.

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 after bathing in shallow lakes where aquatic birds and snails are known to exist.

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.

Treatment and Prevention

The rash from swimmer's itch usually goes away after 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. Still, swimmer's itch will occasionally need treatment with oral or injected corticosteroids. Your healthcare provider may prescribe antibiotics if a secondary bacterial infection is present.

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 microscopic larvae 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. 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.

Treatment and Prevention

There's a delay in how larvae release the antivenom that causes a skin rash, so seabather's eruption can last for up to several weeks. Treatment includes the use of topical corticosteroid creams, oral antihistamines, and, occasionally, oral or injected corticosteroids.

Rubbing the skin makes the symptoms worse, as the larvae release a toxin into the skin as a result of pressure or friction; scratching can lead to bacterial infections. Taking off the contaminated swimwear and washing it before reuse may prevent additional rash and symptoms from developing.

Bikini Bottom Folliculitis 

Wearing wet bathing suit bottoms for long periods can result in deep bacterial folliculitis infections with Streptococcus, Staphylococcus aureus, or P. aeruginosa. The rash is common on the buttocks and armpits.

P. aeruginosa is found in both swimming pools and hot tubs, with some evidence that about two-thirds of them have the bacteria present at any given time. Folliculitis infections can affect multiple people when exposed at public facilities.

Treatment and Prevention

Most cases of bikini bottom folliculitis will go away on their own in a week or two. If not, bikini bottom infection is treated with oral antibiotics. The infection may linger in people diagnosed with diabetes and other chronic health issues.

Bikini bottom folliculitis can be prevented by changing out of wet swimwear promptly and showering immediately. Folliculitis can also occur with diving suits, and this is another reason to clean them with 0.45% lactic acid.

Summary

Ocean rashes, as well as those acquired in freshwater lakes and swimming pools, are symptoms of infection that can arise from different causes, including bacteria, parasites, and larva.

These different causes mean that the appropriate treatments are different, too. Some conditions, like bikini bottom folliculitis, will go away on their own with most people. Others require antibiotic treatment and disinfection of swimming and diving gear.

Talk with your healthcare provider if you have questions about these rashes or experience ocean rash symptoms.