Culprit: the thimble jellyfish
The cause of seabather’s eruption in South Florida and the Caribbean has been identified as the larvae of Linuche unguiculata, or the thimble jellyfish. The adult Linuche (Figure 3) measure 5 mm to 20 mm. They breed between March and September, and the larvae measure about 0.5 mm in diameter, making them invisible to the naked eye.4
These larvae are washed toward the shore by high tides or strong winds. They are small enough to pass through the weave of most swimwear, becoming trapped against the skin. Pressure applied to the skin or changes in osmotic pressure—by evaporation of seawater or showering in fresh water—cause the larvae to discharge their toxin into the skin.6
In a study of cases of seabather’s eruption in the Mexican Caribbean, Segura-Puertas et al7 found that all 3 swimming stages of Linuche (ephyrae, medusae, and larvae) to cause the eruption.
Treatment: antihistamines, topical steroids
Seabather’s eruption can be treated with sedating or nonsedating antihistamines (level of evidence [LOE]=5). While sedating antihistamines may be more antipruritic and less expensive, they should be used with caution if sedation may pose a danger to the patient.
Topical steroids, such as hydrocortisone, may be beneficial. Systemic steroids are reserved for only the most severe reactions. Comfort measures, such as oatmeal baths, may provide some relief of the itching (LOE=5).4
FIGURE 3
Thimble jellyfish
