Diagnosis: Seabather’s eruption
The patient was given a diagnosis of seabather’s eruption (SBE), also called seabather’s dermatitis or sea lice. SBE is an intensely itchy papular-erythematous dermatitis that can develop after an individual has been swimming in the ocean.1
Planula larvae of the scyphomedusae Linuche unguiculata—commonly known as the thimble jellyfish—are to blame for this form of dermatitis.2L unguiculata are most frequently found in the waters of the Caribbean, Gulf of Mexico, southern United States, and South America.1 Cases of SBE are most common in the spring and summer months, peaking in May.3 Those at highest risk include children, people with a history of SBE, and water sports enthusiasts (eg, surfers).4
L unguiculata larvae are small enough that they can make their way through the mesh of swimwear. As the bather gets out of the water, the suit acts as a sieve, with the water draining out and many of the larvae staying behind.1 Once the jellyfish are pressed against the skin, a defense mechanism is triggered and envenomation occurs.1,5
As a result, patients will develop rashes not only in areas beneath their swimsuits, but also in the skin folds, such as the axilla, and between the upper thighs. For surfers, the trouble spots are the chest and abdomen—places where the body rubs up against the surfboard.3,6
Onset does not occur immediately. Rather, it takes several hours for the lesions to develop, and new ones may continue to develop for days.5 Immediate stinging sensations are associated with prior cases of SBE and suggest a sensitization to the antigen.3
Not all reactions are the same. Some people will have a severe response, while others appear to be immune.2 More extreme systemic symptoms, such as fever, chills, nausea, malaise, sneezing, dyspnea, vomiting, headache, abdominal pain, and diarrhea have been seen in children and in cases of extensive envenomation.4,6