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Seabather’s Eruption or Sea Lice - Causes, Symptoms, Diagnosis, and Treatment

Published on Nov 17, 2022   -  4 min read


Seabather's eruption or sea lice is a condition characterized by rashes on the skin due to the entrapment of larvae of jellyfish in the swimming garments.

What Is Seabather’s Eruption?

The seabather's eruption or sea lice was first described in 1949 on the eastern coast of Florida. It was called 'Pica-Pica', which means 'itchy-itchy' in Spanish. It is characterized by itchy and papular lesions on the skin after prolonged exposure to seawater. The main causative agents responsible for this condition are the thimble jellyfish and a sea anemone. These organisms can get easily entrapped between the skin and swimsuit. When trapped between skin and swimsuit, they release various antigenic toxins responsible for the pruritic (itchy) and papular rashes in the host.

The larvae of thimble jellyfish were considered the main culprit earlier; however, recent studies show that the other jellyfish stages are also responsible for this condition. Children below 15 years old are more vulnerable to this condition as they tend to spend more time in seawater than adults. Surfers and individuals who have a prior history of the condition are also at higher risk.

Even though it is also known as sea lice, the term is not so accurate for the condition as sea lice are fish parasites and are unrelated to seabather's eruption. It is also different from a swimmer's itch as a swimmer's itch affects the uncovered areas of the body. In contrast, seabather’s eruption is seen on body areas covered with a bathing suit. Seabather's eruption does not cause many serious symptoms and can be easily treated at home.

What Causes Seabather’s Eruption?

The main causative agents for seabather's eruption are all the free-swimming stages (larvae stages) of thimble jellyfish and the larval stage of the sea anemone, Edwardsiella lineata.

These organisms get entrapped in the bathing suits or hair of the individuals while bathing in seawater. They have specialized stinging cells that get activated by mechanical pressure changes or by osmotic changes due to evaporation or when rinsing off with fresh water. When the swimmer gets out of the seawater, and as the water drains out, these organisms may remain between the swimsuit and skin. These can cause pressure on the jellyfish, leading to the activation of stinging cells. Once the stinging cells are activated, they release toxins to the skin. The initial rash can be due to toxins, and further development of a rash can vary in individuals as it is immune-mediated. Not every individual exposed to the toxins develops severe rashes.

What Are the Symptoms Associated With Seabather’s Eruption?

The symptoms associated with seabather's eruption include;

  • Skin discomfort (tingling sensation) while in water or as soon as when one is out of water.

  • The appearance of extremely itchy rashes, hard or soft bumps, or even blisters. Rashes can be itchy for several hours to weeks and can last up to one to two months.

  • Rashes can be painful in severe cases.

  • The appearance of rashes is confined to the area under the bathing suit, which aggravates while taking a bath in freshwater.

Rare signs and symptoms associated with the condition include;

How to Diagnose a Seabather's Eruption?

The diagnosis of seabather's eruption includes the history of exposure and the physical examination. Laboratory studies, biopsy, or radiographic studies are not so helpful in diagnosing seabather's eruption.

What Is the Differential Diagnosis of Seabather’s Eruption?

The differential diagnosis of seabather's eruption include;

  • Arthropod bites (insects, scorpions, crab, etc.)

  • Folliculitis.

  • Allergic contact dermatitis.

  • Acute urticaria.

  • Swimmer's itch.

  • Seaweed dermatitis.

What Is the Treatment for Seabather’s Eruption?

The treatment for seabather's eruption includes symptomatic or supportive therapy. The supportive therapy includes the usage of 5% acetic acid (diluted vinegar), topical corticosteroids, and systemic antihistamines. When one notices the eruption after removing the costume and taking a shower, the application of diluted vinegar can prevent stinging cells from secreting toxins further. Apply an ice pack to relieve pain.

Topical corticosteroids like 1% Hydrocortisone and antihistamines can be very effective in treating rashes. Systemic corticosteroids are given when symptoms like headache, fatigue, chills, vomiting, etc., are present. Nonsteroidal anti-inflammatory drugs can be given if pain and inflammation are present. However, it is not recommended for children.

Allergies or diseases affecting the immune system can increase the severity of the condition. If the symptoms are getting severe, the patient may require hospitalization even though it is a rare case. There are chances that stinging cells may remain in the swimming garment even after a shower. So, the cloth should undergo machine washing or be washed using hot water and detergent before using it the next time.

What Are the Complications of Seabather’s Eruption?

The rashes from the seabather's eruption may take one to two months to settle. If there is further exposure to the causative organism, the reaction can be more severe due to allergic hypersensitivity of the disease. There have been cases where the symptoms were very severe due to continuous episodes of seabather's eruption. Such individuals should avoid seawater during the seasonal peaks. Wearing swimsuits for an extended period after swimming, taking a bath in freshwater, and mechanical stimulation (wiping with a towel) can complicate the condition.

How to Prevent Seabather’s Eruption?

There is no effective measure to prevent seabather's eruption other than staying out of seawater. It is safe to avoid swimming during seasonal peaks of jellyfish. Avoid t-shirts and one-piece bathing suits as it tends to trap more larvae. One must avoid wearing a swimsuit for a prolonged time and try to take a shower with a bathing suit off whenever possible. One must not rub the affected areas as it can worsen the condition. Do not wear the same clothing again without deep washing.


Seabather's eruption is a condition that can affect any individual. There should be more awareness about this condition. Among people who are so fond of seawater so that people can take appropriate preventive measures and the situation can be less panicky. There are no cases exhibiting symptoms of anaphylaxis or deaths relating to this condition. Seabather's eruption has an excellent prognosis with simple home remedies in most cases.


Last reviewed at:
17 Nov 2022  -  4 min read




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