Slug caterpillar dermatitis is a dermatitis caused by slug caterpillars.


Slug caterpillars live in woods, fields, and grasses. They are about 5cm long, dark brown, with acicular hairs all over their bodies. The hairs have tiny ducts containing alkaline venom. If the hairs pierce the human skin, the venom can be injected into the skin, causing dermatitis. Skin lesions may result from exposure to the clothes contaminated by the toxic hairs.

Signs and Symptoms

After the hairs pierce the exposed skin, such as the face, hands, neck, and forearm, there are pruritus and burning sensation initially, followed by pain and severe pruritus. Subsequently, pinhead sized papules or pea sized wheals occur in the center of the affected site, with peripheral, edematous erythema. The edematous erythema subsides in 6 - 7 hours, leaving central papules. Pruritus and pain relapse repeatedly after scratches. The papules may develop into wheals, and subside in about 1 - 2 weeks. Occasionally, vesicles may occur. If there are some hairs at the same site, large diffuse erythema can occur.

The venomous hairs scattered in clothes can cause extensive lesions. The toxic hairs on the eyelids can cause acute conjunctivitis and keratitis. If the mouth and lips are invaded, severe swelling may occur. There are mild systemic symptoms, but severe patients may die.


If there are a history of exposure and clinical presentations, the disease can be diagnosed.


Topical calamine lotion can be used, and oral antihistamines may be appropriate if there is pruritus after external treatment.