'Sea lice' can cause a big itch for swimmers off the NC coast this summer

The tiny larvae of a thimble jellyfish can cause an itchy rash sometimes called "sea lice" for swimmers along the coast.
The tiny larvae of a thimble jellyfish can cause an itchy rash sometimes called "sea lice" for swimmers along the coast.

The tiny larvae of a peewee jellyfish are causing big problems for some beachgoers this summer, including along the North Carolina coast.

A woman visiting Carolina Beach with her family told WECT News in Wilmington that she thinks her three children are suffering from “sea lice,” a misnomer for an itchy rash that some people get in response to being stung by thimble jellyfish in their larval stage. The rash is also sometimes called seabather's eruption, ocean itch and pika-pika.

Like the tourists who swell the populations of beach towns this time of year, thimble jellyfish appear in North Carolina’s coastal waters each summer, driven by wind and currents. They are more prevalent in warmer waters, such as off Florida and in the Caribbean.

The full-grown thimble jellyfish is only about an inch in diameter, and the larvae are the size of a pin head or a fleck of ground pepper. They float in the water, and most people never see them.

If they get trapped inside a swimmer’s clothing — under a T-shirt or snug bathing suit, for instance — or in a crease of skin, the pressure causes the stinging cells surrounding the larvae to fire.

Some people feel the sting when it happens, noticing a mild prick. Others don’t even notice.

Read Next

Those who are sensitive to the sting or get a large number of them may develop a rash around the site within 24 hours. It can last a week. Some people develop more serious symptoms, including fever, chills, nausea, headache and weakness. Anyone who develops swelling or trouble breathing should seek emergency medical care.

“For most people, it’s not dangerous, it’s just a pain in the butt,” said Larry Cahoon, a marine biology professor at UNC-Wilmington. “They’re just defending themselves. They’re not going to eat you.

“It is annoying. It’s the last thing you want to deal with when you go to the beach. It’s like hanging out in your backyard and the mosquitoes bite you.”

There is no repellent known to keep the larvae from stinging. To reduce the likelihood of being stung or developing a reaction, swimmers are advised not to wear extra clothing such as T-shirts into the ocean. After swimming, change out of your bathing suit as soon as possible. Avoid towel-drying, as rubbing can cause the firing of the stinging cells, or nematocysts, that remain on the skin. Rinsing off in fresh water can also cause them to fire.

If you know you’ve been stung, apply vinegar to the skin to neutralize the nematocysts that remain on the skin but haven’t yet fired. Wash bathing suits thoroughly, in detergent.

Anti-itch creams can help relieve the rash, and antihistamines can provide relief if needed.

Cahoon, who lives at the coast, says people shouldn’t let a spineless, nearly invisible creature ruin their vacation.

“It’s not a good reason not to come to the beach,” he said.

Related stories from Raleigh News & Observer