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Everything You Need To Know About Sea Lice and Seabather’s Eruption

Sea lice aren’t really lice, but these tiny creatures can trigger an unpleasant allergic reaction

Kids playing in ocean/sea waves

If you’re looking to spend some time on the beach this summer for a well-deserved seaside vacation, you’ll need to make sure you have all the essentials packed and ready to go. Sunscreen. Water. Enough healthy snacks to go around. Maybe you even keep an eye out for pesky sea lice and signs you’ve been stung.

Wait ... what?

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Before you completely avoid open ocean water, know that sea lice and their associated rash, known as seabather’s eruption, aren’t much of a serious concern. Sea lice aren’t like your typical head lice. Although seabather’s eruption can be uncomfortable, it’s typically easy to spot and fairly easy to treat.

Urgent care physician Allan Capin, MD, explains just what sea lice are and how to treat the rash commonly associated with these creatures.

What is seabather’s eruption?

Seabather’s eruption is a skin rash that develops when tiny, transparent larvae from jellyfish or sea anemones hitch a ride on your swimsuit or other clothing. These tiny creatures are almost impossible to see with the naked eye as they float on the surface of the water.

Although these larvae are commonly called “sea lice,” this term is misleading. These ocean dwellers aren’t related to head lice. They don’t intentionally bite you or feed off your blood. Instead, these larvae release a stinging toxin into your skin as a defense if they remain trapped in your swimsuit long enough or become pressed against your skin.

“Seabather’s eruption is an allergic reaction to the toxins released by sea lice larvae,” explains Dr. Capin. “Children tend to have a more severe reaction than adults, but it affects people of all ages.”

And if you get seabather’s eruption more than once, the rash could get worse each time. Fortunately, most people won’t experience anaphylaxis (a life-threatening allergic reaction), even if they have other allergies.

What does a sea lice rash look like?

If you’ve been swimming with sea lice, you’ll likely develop a reaction within 24 hours. Sometimes, the reaction can occur minutes after getting out of the water or even hours later.

“You can often identify seabather’s eruption by looking at the pattern of the rash,” explains Dr. Capin. “A sea lice rash affects areas covered by your bathing suit, so you don’t usually see it on your legs, arms, hands and feet. But you might also find it on your head, in facial hair or places where you have a lot of body hair and sea lice become trapped or pressed against your skin.”

A sea lice rash is usually:

  • Extremely itchy.
  • Red and raised, resembling acne pimples, blisters or welts.

Some people, especially children, can have systemic (whole-body) symptoms, including:

Where and when does seabather’s eruption happen?

The larvae that cause seabather’s eruption only live in saltwater oceans and seas, not freshwater lakes. Sea lice are also most common along the coast of Florida and the Caribbean. You’re more likely to encounter the problem from March through August, with peaks in May and June.

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“Sea lice larvae can be unpredictable because they come and go with ocean drifts and the Gulf Stream,” notes Dr. Capin. “If you got seabather’s eruption at a particular beach last year, that same beach might be free and clear this year — and vice versa.”

Can I avoid seabather’s eruption?

There are a few ways you can skip a potential run-in with sea lice — or at least prevent a severe rash:

  • Read health reports: Check for beach updates from your local health department. If sea lice have been reported, notices will likely be put in place. You’ll want to avoid swimming in that area until it’s safe to do so.
  • Resist rubbing: An early sign of sea lice is tingling under your swimsuit. Don’t rub or scratch the area, as you could aggravate the larvae and make the rash worse.
  • Remove swimwear and shower: As soon as possible after swimming, remove all swimwear, including swimsuits and rash guards, and rinse off with unaffected salt water right away. Fresh water can sometimes irritate sea lice larvae and cause them to sting by throwing off their chemical imbalance. Once you've rinsed off with salt water, you should be able to shower safely. The length of the shower and water temperature don’t matter, but removing your swimwear first is a must.
  • Wash swimwear: After swimming, thoroughly wash all swimwear to remove any lingering larvae. Don’t leave your swimwear out to dry and then wear them the next day unless you’ve washed them thoroughly first. You also don’t want to lend anyone else your swimwear either. Although seabather’s eruption isn’t itself contagious, if there are lingering larvae on the swimwear, they can still transmit their toxins to someone else and cause a separate reaction.

How do you treat a sea lice rash?

You can find some relief from seabather’s eruption with at-home treatments and remedies, including:

  • Antihistamines: Because a sea lice rash is an allergic reaction, an antihistamine can help with your symptoms. “Some antihistamines can cause drowsiness, so be aware of this side effect before taking these medications,” states Dr. Capin.
  • Ice packs: Ice can help with inflammation and itching, and you can safely use it in combination with other treatments. Cover the ice pack with a cloth, and don’t ice any area for more than 15 minutes at a time.
  • Skin protection: Try to avoid scratching the rash — difficult as that may be. Scratching could damage your skin or cause an infection. “If your child can’t keep their hands away, consider having them wear soft gloves until the rash improves,” suggests Dr. Capin.
  • Steroid creams: Over-the-counter anti-itch creams that contain hydrocortisone can help control inflammation and itching.
  • Vinegar: Applying vinegar with 5% acetic acid onto your skin after swimming can help prevent some of the larvae from releasing their toxin. This extra step might help deactivate some of the larvae before you get to the shower.

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In some cases, a prescription medication is necessary to clear up seabather’s eruption. “Doctors may prescribe a stronger medication if the rash affects your face, groin or armpits,” says Dr. Capin. “These areas tend to be more sensitive and more prone to severe inflammation and itching.”

How long does seabather’s eruption last?

A sea lice rash usually goes away within two weeks, but it can take up to a month to clear up completely depending on the severity of your rash and how quickly your body heals. For most people, the worst part is the itching and discomfort. But anytime you have a rash or break in your skin, there’s the added risk of infection.

If you notice any of these possible signs of infection, contact a provider:

  • Drainage or pus.
  • Feeling of warmth on your skin.
  • Fever of 100.4 degrees Fahrenheit (38 degrees Celsius) or higher.
  • Pain.
  • Red patches or streaks.
  • Swelling.

Don’t let sea lice ruin the fun

Seabather’s eruption usually isn’t serious, but its name and nature raises a lot of red flags, especially for beach-going parents and caregivers looking to take a load off. Fortunately, you can usually avoid this nuisance by monitoring health reports and showering soon after you swim.

“If you plan to swim in the ocean, take a few precautions first,” advises Dr. Capin. “Choose a spot that has a private area to change and shower after swimming, and you can focus on relaxing, rather than a rash.”

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