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. But microscopic organisms cause special types of itchy rashes after swimming, either in saltwater (the ocean) or freshwater (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, 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 includes the use of topical corticosteroid creams, oral antihistamines, and the occasional need for 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. These species of schistosomes are not the same as 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 shallow lakes where aquatic birds or freshwater snails are known to exist. There isn't a way to prevent getting swimmer's itch other than avoiding contact with contaminated lakes and rivers.

Swimmer's itch is most common in the Mid-Western United States but also occurs in warmer climates such as Texas as New Mexico.

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.

Diving Suit Dermatitis

If you wear a scuba diving suit, you may end up a diffuse red rash caused by a common bacterium, Pseudomonas aeruginosa. The cause is that the bacteria can grow in a neoprene diving suit if it isn't cleaned after every use with 0.45 percent lactic acid. This can be prevented by proper care of the suit and shower immediately after wearing it. This rash can require antibiotics to clear up.

Bikini Bottom

Wearing wet bathing suit bottoms for long periods can result in deep bacterial folliculitis infections with Streptococcus or Staphylococcus aureus. This can be prevented by changing out of wet swimwear promptly and showering immediately. It can also occur with diving suits and is another reason to clean them with 0.45 percent lactic acid. Bikini bottom infection is treated with oral antibiotics.