Seabather's eruption is an itchy rash caused by a nearly invisible marine pest known as sea lice, which lurks in warm oceans, including the Gulf of Mexico and the Caribbean during the summer. Severe cases can result in flu-like symptoms.
ABC station KTRK-TV of Houston has reported that sea lice outbreaks are on the rise this year, especially at beaches along the Gulf of Mexico.
"Outbreaks of seabather's eruption occur intermittently between March and August, but they appear to peak during early April through early July," according to the Florida Department of Health. "Seabather's eruption appear to be caused by shifts in South Florida's currents, with the highest incidence of cases in such areas as Palm Beach County and Northern Broward County, where the Gulf Stream passes closest to shore."
Sea lice are no bigger than a speck of ground pepper, according to the Florida DOH, and are the larvae of adult jellyfish. (What are commonly called sea lice are not the parasitic sea lice that plague farmed salmon and other saltwater fish.) The nearly invisible baby jellyfish get caught between swimmers' skin and their bathing suit, other clothes and even hair, making the larvae sting.
According to Parks and Recreation officials for Palm Beach County, "Some people do experience a prickling sensation while in the water, though itching usually starts several hours after being in the water and lasts two to four days but can last as long as two weeks."
Palm Beach County has posted sea lice signs to warn swimmers when there are outbreaks at its beaches. Other seaside Florida counties will hang purple flags at beaches to signal the presence of marine pests such as sea lice.
The rash from sea lice, while a nuisance, often goes away on its own. The Florida DOH recommends treating the rash with an antihistamine or hydrocortisone cream. Bathing in colloidal oatmeal and applying calamine lotion can also help soothe the rash or itchiness.
Beachgoers can avoid sea lice by wearing as little clothing as possible in the water. Changing out of bathing suits as soon as possible and washing bathing suits well can also help prevent severe bouts of seabather's eruption, according to the Florida DOH.