Headed to the Shore? Beware of sea lice.

Todd Shevlin was vacationing with his family in Ocean City, Md., last week when he came down with flu-like symptoms shortly after getting out of the waves. Twelve hours later, the Devon man noticed a rash on his hands and feet that kept getting worse. Doctors determined that Shevlin was having a bad reaction to sea lice.

"My body did not like this particular creature," said Shevlin, 40. "It is just a matter of fighting through it at this point, and I hope it goes away in less than a month."

This summer has seen outbreaks of sea lice reactions along beaches in states including New Jersey, Delaware, Florida, and North Carolina as the waters warm.

Sea lice are not actual lice but the larvae of jellyfish, most likely thimble jellyfish, said Paul Bologna, professor of biology and the director of the marine biology and coastal sciences program at Montclair State University.

The rash of tiny bites they leave behind resembles that of head lice, thus the name, said Bologna. "They get into your bathing suits, they are stuck against you and stinging you as they interact with your skin." The condition is also known as seabather's eruption.

There are many varieties of sea lice that can make swimmers uncomfortable, including blue crab larvae, which come in huge swarms and hold onto anything they can — including hair — when they are ready to settle, he said. They are likely carried closer to shore by winds.

Symptoms can range from itchy bites and hives, particularly along bathing suit lines, that can last around two weeks, to more severe reactions that include headaches, nausea, vomiting, and diarrhea, Medscape reported.

Both Shevlin and his 7-year-old son, Oliver, who did not have as bad of a reaction, developed the telltale rash, said Laura K. Reed, Shevlin's wife. She ended up bite-free and attributes it to a dunk in the pool shortly after returning from the beach. Shevlin, who is still dealing with after-effects – including some limited feeling in his fingers and toes — said he might skip the warm ocean waters and stay poolside on their next trip.

The bites are common this time of year when the water is warmer, said Nazanin Saedi, assistant professor of dermatology at Jefferson University Hospitals. The rash can last for days, she said.

Best advice is to take off your bathing suit and rinse off with fresh water as soon as possible after getting out of the ocean, she said.

"Make sure to wash the bathing suit thoroughly," she added. Wring it out and leave it out to dry, which will kill any remaining larvae.

Treat the bites like you would any other insect bite, she recommended. Take an oral antihistamine if needed for swelling, or use a topical steroid cream without any extra ingredients that may cause more irritation.

For more serious reactions, call your doctor for a prescription steroid cream, she said.

Last week in New Jersey, Ocean City lifeguards were fielding questions from some bathers about the itching they were experiencing after swimming, said Shanin Theiss, a senior lifeguard. This year's outbreak is one of the worst he can recall in the 25 to 30 years he has been coming to the beach as a swimmer and now lifeguard.

"I picked some of them off me," he said. "I could see clear little objects in the water and on the paddle board."

Theiss said the larvae probably blew in with the winds and currents. It was a 48-hour phenomenon, he said.

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Bathers at the Mississippi Avenue beach in Atlantic City also came pouring out of the water last week with tiny sea lice clinging to their hair, said Steve Downey, chief of the Atlantic City beach patrol.

"They were blatantly all over the kids," he said. With the warmer waters and a northeast breeze, the larvae must have drifted toward shore, Downey said.

"They've got this little jellyfish body and little pincers at the end. You would barely see them, but they were there," said Downey.

The incident was isolated to the Mississippi Avenue beach and there hasn't been a report since, he said.

Further north, in Ocean Grove, Victoria Morgan, 33, of  Brooklyn, N.Y., spent Sunday at  the beach, swimming with friends.

"That evening, I noticed red bites," Morgan said.

"It hasn't been particularly itchy," she said, noting that she was already taking allergy medicine, which was probably helping. "It is sensitive skin, and it is taking a while to heal."

Morgan said the encounter was a "chance experience" and she will be back in the water soon.

"It is the same as mosquito bites as far as I am concerned. It's par for the course," she said.

The bottom line, Theiss said, is that the Atlantic Ocean is home to lots of creatures and organisms.

"It is their playground; we are playing in it," he said.