What are sea lice, and do I have to worry about them in the Gulf of Mexico?

Visitors to Mississippi Coast, Alabama and Florida beaches have long been enthralled by their marine biodiversity, promising once-in-a-lifetime opportunities to spot dolphins, sea turtles and occasionally sharks deep in the Gulf of Mexico.

The Biloxi-Gulfport metro’s heavy tourism season is the summer, when visitors come from across the U.S. to enjoy the man-made beaches and murky Mississippi Sound. Two Coast cities were even named some of the best beach towns in the U.S. recently.

Less likely to be on that oceanic bucket list are sea lice.

Be warned: These crustaceans are not only bountiful, but can leave a most uncomfortable souvenir for its hosts.

Sea lice outbreaks, however, are more common in the Atlantic near tourist towns like Myrtle Beach and are more rare in the Gulf of Mexico, with the last one reported in 2018.

Here’s what you need to know about these critters, also dubbed “seabather’s eruption.”

They aren’t actually insects

Sea lice are copepods — a microscopic type of crustacean related to crabs, shrimp and lobsters. With nearly 15,000 identified species, the creatures are found anywhere there’s water and are a vital part of the food chain for many types of birds, fish and whales.

Now that the science is out of the way, what exactly are sea lice?

They’re a small type of jellyfish still in their immature form and can easily get trapped in hair or bathing suits.

”When you get out, the water drains off of you, but the larvae stay behind. Your bathing suit rubs against your skin, causing the larvae to sting you and inject their toxin,” is how WebMD.com explains the sea lice plan of attack.

Salmon are also plagued by a type of sea louse, but it’s an unrelated type of parasite.

Impossible to ignore, but not life threatening

A tingling sensation in areas where the larvae got trapped — most commonly under clothing and in hair — could be the first signal of a sting. Itching could start a short time later, according to Riverchase Dermatology, which has offices along the Florida coast.

The rash usually appears between four and 24 hours after swimming. A small number of people may develop additional symptoms including chills, fatigue and nausea.

How can I avoid being stung?

Jellyfish larvae are most abundant between April and July, so chances of an outbreak increase during those months. Pay attention to weather reports, too, since wind currents and tidal changes can bring the larvae closer to shore in greater numbers.

Don’t wear a T-shirt or other top while in the ocean, as it gives sea lice more surface area to latch onto.

Wearing tight bathing suits or putting one on that hasn’t been washed or dried can also up the chances of a sea lice assault, since the stinging cells aren’t alive and can cling to clothing.

Treating a sea lice sting can be done at home in several ways

Riverchase Dermatology has several suggestions on its website for people who have been stung

• Wrap ice packs in a towel or cloth and place them on the stung areas
• Take a non-steroidal, anti-inflammatory drug such as ibuprofen to help relieve pain and inflammation
• Apply calamine lotion or an over-the-counter topical corticosteroid cream according to the package directions to ease the itching
• Take an antihistamine to calm the allergic reaction

Sun Herald reporter Mona Moore contributed to this report.

This story was originally published July 25, 2023 at 11:33 AM with the headline "What are sea lice, and do I have to worry about them in the Gulf of Mexico?."