What Is Sea Lice

Contents

Sea lice is skin irritation due to the trapping of small jellyfish larvae underneath bathing suits in the ocean. Pressure on the larvae causes them to release inflammatory, stinging cells that cause itching, irritation, and red bumps on the skin. Doctors also call this sea bather’s eruption or pica-pica, which means “itchy-itchy” in Spanish.

What Are Sea Lice Bites and How Do You Get Rid of Them?

Sea lice is skin irritation due to the trapping of small jellyfish larvae underneath bathing suits in the ocean. Pressure on the larvae causes them to release inflammatory, stinging cells that cause itching, irritation, and red bumps on the skin. Doctors also call this sea bather’s eruption or pica-pica, which means “itchy-itchy” in Spanish.

Although they’re called sea lice, these larvae have no relation to the lice that cause head lice. They aren’t even sea lice — actual sea lice only bite fish. However, the term has stuck over time.

While the skin irritation is usually mild to moderate, some people can experience more severe side effects, such as a high fever in children. While the sea lice bites were first identified in areas of the southern coast of Florida, they also have been identified in tropical and subtropical areas around the world. Outbreaks are usually worse from March to August.

You can experience the symptoms of sea lice bites almost immediately after getting in the water. You may describe the initial symptoms as “prickling” sensations. After this time, the skin will usually start to itch. Additional symptoms may include:

headaches
lethargy
nausea
rash that appears underneath where a bathing suit would be
red bumps that may come together and resemble a large, red mass

The jellyfish larvae also have a particular liking for hair, which is why many people may find the bites begin on the back of their necks. However, it should be emphasized that even though they may cling to hair, they’re not head lice.

The rash usually lasts about two to four days. However, some people may experience a rash from sea lice bites for up to two weeks. Children are especially prone to experience severe symptoms associated with sea lice bites, including nausea and high fevers.

Sea bather’s eruption usually occurs during warm summer months when winds bring thimble jellyfish and anemone larvae near the shoreline. Sea lice bites seem to be especially common in Palm Beach and Broward counties in Florida where Gulf Stream winds blow currents.

When you swim in the ocean, the larvae become trapped inside your swimsuit. The larvae have stinging cells known as nematocysts. When the larvae rub against your skin, you experience the skin irritation known as sea lice bites.

Wearing tight bathing suits makes the bites worse because of the added friction. So, does rubbing a towel against the skin.

You can also get sea lice bites if you put a swimsuit back on that you haven’t washed or dried. Because the stinging cells aren’t alive, they can stay on clothing.

You can usually treat sea lice bites with over-the-counter treatments. Examples include applying 1 percent hydrocortisone cream to areas of the bites two to three times a day for one to two weeks. This can help to reduce itching and inflammation. Other steps you can take include:

applying diluted vinegar or rubbing alcohol to irritated areas to soothe them
applying cloth-covered ice packs to the affected areas
taking nonsteroidal anti-inflammatory drugs (NSAIDs), such as ibuprofen and aspirin, to reduce pain and inflammation (however, children under age 18 shouldn’t take aspirin)

Sometimes, a person can have a severe reaction to sea lice bites and need to seek medical attention. A doctor may prescribe oral corticosteroids, such as prednisone.

With treatment, sea lice bite symptoms will go away within four days.

Sea lice bites aren’t contagious. Once you have the sea lice bites rash, you can’t pass it along to another person.

However, it’s possible that if you loan out your swimsuit without washing it, another person could get a rash from the cells. This is why you should wash your swimsuit and dry it in warm heat after washing.

If the stinging jellyfish larvae are present in the ocean, there’s little you can do to prevent getting bitten other than staying out of the water. Some people have tried to apply barrier creams to the skin or wear wet suits to avoid the bites. However, most people are still affected.

Doctors do know that swimmers and snorkelers are more vulnerable to the effects of sea lice bites because the jellyfish seem to live on the surface of the water.

Pay attention to lifeguard stations and warnings before getting in the ocean. Beaches will often issue warnings if sea lice infestations are affecting people.

Also, change your swimsuit quickly after getting out of the water. Wash your skin in seawater that is known to not have jellyfish larvae present. (Washing the skin in freshwater or vinegar immediately after leaving the water can make the bites worse.)

Gently pat your skin dry (don’t rub) and wash all bathing suits after wearing.

Sea lice bites can range from a nuisance in adults to the cause of nausea, fever, and more severe symptoms in children. While the rash typically goes away with time and isn’t contagious, you may wish to try over-the-counter treatments, like hydrocortisone creams, to reduce itching. If that doesn’t work, check out these other great remedies for itching.

Last medically reviewed on August 22, 2018

How we reviewed this article:

Healthline has strict sourcing guidelines and relies on peer-reviewed studies, academic research institutions, and medical associations. We avoid using tertiary references. You can learn more about how we ensure our content is accurate and current by reading our editorial policy.

Rademaker M. (2014). Sea bather’s eruption.
dermnetnz.org/topics/sea-bathers-eruption/
Rossetto AL, et al. (2015). Seabather’s eruption: Report of fourteen cases.
10.1590/0001-3765201520130468
Russell MT, et al. (n.d.).
floridahealth.gov/diseases-and-conditions/food-and-waterborne-disease/_documents/sea-lice-or-sea-bathers-eruption.pdf
Sea lice. (n.d.).
palmbeach.floridahealth.gov/programs-and-services/infectious-disease-services/_documents/sea-lice-info-brochure-2017.pdf
Sea lice/jellyfish. (n.d.).
arphs.govt.nz/health-information/healthy-environments/sea-lice-jellyfish

Sea Lice Bites

After swimming in warm ocean waters, some bathers discover a red itchy rash on the skin under their bathing suit. Some people call the critters that gave them this rash “sea lice.” But they’re not lice at all. They’re thimble jellyfish larvae.

Real sea lice are parasites that feed on the blood of salmon and other fish. They don’t bite humans. For some reason, though, in the 1950s, residents of coastal areas began to call the stings of jellyfish larvae “sea lice bites.” The name just stuck. But that’s not the only name. Some doctors call the skin irritation “seabather’s eruption.”

What Do the Stings Look and Feel Like?

Jellyfish larvae sting from small, very itchy red bumps on your skin. The bumps may change into blisters.

The rash typically appears between 4 and 24 hours after your swim. You might feel a slight prickling sensation in the water when the larvae release their toxins.

You’ll often see the rash on areas of your body that your bathing suit covers. You might also find spots on your arms, legs, neck, and in your armpits.

Sea Lice vs. Swimmer’s Itch

This rash looks a lot like a swimmer’s itch. But they’re not the same thing.

In swimmer’s itch, infected snails release tiny parasites into the water. Those critters burrow under your skin and cause an itchyallergic reaction.
The rash usually forms on skin that’s outside your bathing suit. And you’ll only get it in freshwater such as lakes.

What Other Symptoms Do They Cause?

In adults, an intensely itchy rash is often the only symptom. Children can have more body-wide symptoms like:

How Long Does the Rash Last?

Usually, the rash fades within two weeks. In some people, it can stick around for a few extra weeks.

Are Jellyfish Larvae Toxins Harmful?

Jellyfish larvae toxins aren’t dangerous to healthy people. Rarely, do children with allergies or a weakened immune system have a more severe reaction. Take your child to the doctor if she has a fever and chills along with the rash.

How Do You Treat the Rash?

Swimmers use a variety of home remedies to relieve the itch of “sea lice,” including rubbing alcohol and meat tenderizer. But there’s no evidence these work. Lice treatments won’t help either, since it’s not really like you’re dealing with.

An antihistamine pill or steroid cream can help relieve the itch. If you have a more severe case, your doctor may prescribe a steroid pill or shot. You can also apply colloidal oatmeal cream or calamine lotion to soothe the itch while the rash heals.

How to Avoid the Rash

The only way to avoid stings is to stay out of the water during peak season. Use caution if you swim or dive along the coast of Florida or the Caribbean between May and August. That’s when jellyfish release their larvae into the water.

Even the best precautions when you swim in these areas may not protect you. Jellyfish larvae are as small as specks of black pepper, and just as hard to see when they float in the ocean. And you may not see any larger adult jellyfish nearby.

Protect yourself when you dive by wearing a wetsuit. Don’t wear a t-shirt or one-piece bathing suit into the ocean, because it can trap the larvae inside. Bathing suits made from tightly woven fabrics are better at keeping out jellyfish larvae than loosely woven fabrics.

Remove your wetsuit or bathing suit when you get out of the water, and rinse off in the shower. The more exposure you have to the jellyfish larvae toxins, the worse the rash will get. Wash your bathing suit in hot water and put it in the dryer to kill any larvae trapped in the fabric.

References

Alaska Department of Fish and Game: “What Are Sea Lice?”

CDC: “Swimmer’s Itch FAQs.”

Divers Alert Network: “Debunking the Sea Lice Myth.”

Florida Department of Health: “Sea Lice or Seabather’s Eruption.”

Medscape: “Seabather’s Eruption.”

StatPearls: “Seabather’s Eruption.”

Medical Reviewer: Debra Jaliman, MD

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What Is Sea Lice