What Are Sea Lice, and How Do You Avoid Their Red, Itchy Rash?


Florida beachgoers got a bit of a scare this week when Pensacola health officials issued warnings about stinging sea lice and the irritating, red rash the critters can cause. News stories about the warnings have gone viral—along with an itch-inducing photo of just such a rash—prompting concerns nationwide.
So what are sea lice, exactly, and how concerned should you be if you’re going to the beach anytime soon? That depends on where, exactly, you’re headed. The good news, though, is that the tiny animals are more of a nuisance than a serious danger. Here’s what health experts want you to know about this developing story.
Sea lice are actually jellyfish
The term sea lice was inappropriately coined by residents who suffered strange rashes after swimming in coastal waters in the 1950s, according to the Florida Department of Health. (There is such a thing as actual sea lice, it turns out, but they are tiny parasites that affect fish, not humans.)
The rash that humans tend to get, on the other hand, “is caused by miniature jellyfish larvae trapped under bathing suits when in the water,” states a 2017 brochure available on the Health Department’s website.
“If pressure occurs from exercising, surfboards, lying on the beach, etc., stinging cells are released and cause itching, irritation, and welts,” the brochure continues. The larvae also like to hang out in people’s hair, so the back of the neck—where hair hangs down and touches the skin—is a common place for lesions.
Health officials stress that these jellyfish larvae are not related to head lice, which are common among young children and can be quite contagious. In fact, the larvae cannot survive out of warm salt water and don’t remain on a swimmer’s body once they’re on dry land, the Pensacola News Journal reports.
They’re common throughout Florida
The rash associated with sea lice—also known as sea bather’s eruption—has been documented along Florida’s coastline for several decades, according to the state’s Department of Health. Complaints tend to peak from March through August, and outbreaks appear to be caused by shifts in ocean currents.
The frequency and intensity of sea-lice outbreaks has gotten worse in recent years, health officials say, based on the number of cases reported. Because most people treat themselves, however, there aren’t any good estimates on how prevalent these rashes really are.
The hardest hit areas are in the southern part of the state—in Palm Beach and North Broward counties—where the Gulf Stream passes closest to the shore.