Cutaneous Larva Migrans (CLM), or creeping eruption, is a parasitic skin infection caused by nematode larvae entering the upper layers of human skin. This condition is common in tropical and subtropical environments, often acquired while traveling to warm climates. Although the infection is generally self-limiting, it causes intense discomfort and a distinct, visible skin reaction. The name “creeping eruption” describes the rash’s appearance: a migratory track moving slowly across the skin’s surface.
The Parasitic Origin
The cause of creeping eruption is the larval stage of hookworms, primarily Ancylostoma braziliense and Ancylostoma caninum, which typically infest the intestines of dogs and cats. These larvae are not adapted to complete their life cycle in a human host.
The cycle begins when infected animals pass eggs in their feces onto the ground. In warm, moist, sandy soil, these eggs hatch into infective larvae. Transmission occurs when exposed skin contacts this contaminated soil or sand.
The larvae penetrate the skin but are unable to reach the deeper layers. This forces them to remain trapped in the epidermis, the outermost skin layer, where they begin to migrate.
The areas most frequently affected are those that commonly contact the ground, such as the feet, legs, buttocks, and hands. The larval movement triggers an immune response that manifests as the distinctive rash.
Identifying the Characteristic Rash
The most telling sign of creeping eruption is the intensely itchy, raised, and reddish skin lesion. This rash typically follows a snakelike or serpentine path, representing the larvae’s movement just beneath the skin’s surface. The lesion is narrow, measuring about 2 to 3 millimeters wide, and may be felt as a thread-like structure upon palpation. The severe itching is often the most significant symptom and may worsen at night.
The term “creeping eruption” refers to the slow, visible migration of the track, which advances as the larva moves. The larvae typically move at a rate of 1 millimeter to 2 centimeters per day. The winding track is a visible sign of the body’s allergic and inflammatory reaction to the migrating parasite.
The rash begins as a small red bump at the entry site, usually within a few days of exposure. Severe scratching of the itchy area can lead to secondary bacterial infections, such as cellulitis. In rare instances, the migration may trigger an allergic pulmonary reaction known as Löffler syndrome.
Treatment and Recovery
Although the infection is self-limiting, medical treatment is recommended to alleviate symptoms and kill the migrating larvae quickly. Anthelmintic medications, which target parasitic worms, are the standard therapeutic approach.
For widespread or severe infections, oral anti-parasitic drugs like albendazole or ivermectin are highly effective and often preferred. Albendazole is typically given daily for three to seven days, achieving high cure rates. Ivermectin is also highly effective, often achieving results with a single dose.
Topical treatment, such as thiabendazole cream or solution, can be used for localized lesions. This application helps avoid systemic side effects. Symptomatic relief from severe itching is achieved with antihistamines or topical corticosteroids, administered alongside the anti-parasitic medication. With effective treatment, intense itching subsides within 48 hours, and lesions resolve within one week.