Jellyfish Stings 
Basics
Two types of stinging jellyfish are seen floating in the coastal waters of North America: the smaller sea nettle and the more rare, more dangerous, Portuguese man-of-war, whose poison can be fatal.
The tentacles of jellyfish have many stinging nematocysts, which contain a hollow poisonous tip and hooks. The hooks hold the jellyfish onto the victim while the nematocysts discharge the toxic venom.
Clinical Manifestations
Victims of a common jellyfish sting usually describe a stinging or burning sensation.
The sting of the Portuguese man-of-war is more painful than that of a jellyfish. It has been described as feeling like being struck by a lightning bolt, and some victims dread it more than a shark bite (Fig. 29.24).
There have been reported cases of anaphylactic reactions and fatalities from both sea nettle and Portuguese man-of-war stings.
Description of Lesions
The shape of the lesions, which resemble linear welts that develop at the site of contact, often give the victim the appearance of having been whipped (Fig. 29.25).
Lesions may fade or may blister and become necrotic depending on the amount of injected venom and the victim's sensitivity.
Diagnosis
The diagnosis is based on the reported sting occurring in an endemic area and its characteristic eruption.
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Management 
Point to Remember Basics
This intensely pruritic eruption develops under swimwear, presumably because the responsible larvae become trapped under the garments.
The eruption occurs several minutes to 12 hours after exposure to the larvae of the thimble jellyfish (Linuche unguiculata) in the saltwater off the coast of Florida and in the Caribbean.
This condition has also been noted off of coastal Long Island, New York, where it has been reputedly caused by the larvae of a sea anemone.
Clinical Manifestations
Erythematous macules and papules occur under swimwear (Fig. 29.26A,B). The eruption has a similar distribution as seen in hot tub folliculitis (see Fig. 16.12).
The pruritus is worse at night and tends to prevent the patient from sleeping.
Diagnosis
Differential Diagnosis 
Helpful Hints Basics
As the name suggests, cutaneous larva migrans is a cutaneous eruption that creeps or migrates in the skin. It results from the invasion and movement of various hookworm larvae that have penetrated the skin through the feet, hands, lower legs, or buttocks.
Ancylostoma braziliense, Ancylostoma caninum, Ancylostoma ceylanicum, Uncinaria stenocephala (dog hookworm), Bunostomum phlebotomum (cattle hookworm), Ancylostoma duodenale, and Necator americanus are the primary hookworms that cause cutaneous larvae migrans in the United States.
The adult hookworm (nematode) resides in the intestines of dogs, cats, cattle, and monkeys. The feces of these animals contain hookworm eggs that are deposited on sand or soil, hatch into larvae if conditions are favorable, and then penetrate human skin which serves as a “dead-end” host.
At greatest risk are gardeners, farm workers, and people who sunbathe or walk on sandy beaches by the seashore.
Larva currens, a distinct variant of cutaneous larva migrans, is caused by Strongyloides stercoralis and may produce visceral disease. Visceral larva migrans is caused by another species of hookworm.
Clinical Manifestations
This benign eruption is usually pruritic and self-limited because the larvae usually die within 4 to 6 weeks.
Lesions have a characteristic curvilinear, serpentine shape (Fig. 29.27).
Areas that come into contact with sand or contaminated soil, most commonly the feet (farmers) or buttocks (sunbathers on nude beaches) are affected.
Diagnosis
The diagnosis is based on the characteristic clinical appearance.
If the patient has been vacationing on the beach in an area endemic for cutaneous larva migrans, consider the condition when diagnosing a local itchy eruption on one foot.
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Outline