ACMT Toxicology Visual Pearls: Caterpillar Envenomation

D – Transparent tape application and removal over the area of dermatitis

Caterpillar Envenomation

While most caterpillars of the order Lepidoptera in the US are not dangerous to humans, some have evolved defense mechanisms including venoms administered by the urticating hairs or spines. Humans who contact these caterpillars may develop dermatitis, itching, erythema, and rarely systemic effects. Erucism refers to cutaneous dermatitis from contact with caterpillar hairs and spines, while lepitopterism refers to the systemic adverse effects. Initial treatment includes the removal of embedded hairs or spines using tape such as transparent tape [1,2,3]. The photograph contains an example of one such specimen, the buck moth caterpillar Hemileuca maia.

In 2018, US Poison Control Centers received 2,816 cases of caterpillar exposures, with over 40% occurring in people 19 years old or younger and children 5 years or younger accounting for 20% of all cases [4]. Seasonal epidemics have been reported [5].

What is the clinical presentation of erucism [1, 2, 3, 6]?

• The presentation depends on the caterpillar species.
• In the United States, most native venomous caterpillars contain histamine-like toxins or stimulate the release of endogenous histamine.
• Dermatitis, welts, itching, and burning sensation are common.
• Systemic effects are rare in caterpillars native to the United States but may include generalized urticaria, headache, conjunctivitis, vomiting, bronchospasm, dizziness, diaphoresis, and abdominal pain.
• South American caterpillars of Lonomia moths produce a toxin that can result in “hemorrhagic syndrome”, which may manifest as consumptive coagulopathy and renal failure.

How do you manage erucism [1, 2, 3, 6]?

• Place transparent tape over the affected area to remove embedded hairs or spines, using a new piece of tape each time.
• Apply ice packs to reduce the burning sensation; isopropyl alcohol wipes may also enhance cooling
• Hydrocortisone cream and antihistamine cream may provide relief
• Consider topical anesthetics, such as lidocaine 2-4% ointment, for pain relief
• Provide local wound care and tetanus prophylaxis
• Ocular lesions require extensive irrigation and ophthalmology follow up
• Watch for anaphylactoid/anaphylactic symptoms and treat them appropriately

Bedside Pearls

• Caterpillar envenomations frequently present with dermatitis, itching, and burning at the site of exposure to hairs or spines.
• Removal of the hairs or spines with tape is a key component of management.
• Systemic symptoms are rare in most species native to the United States.
• Local pain relief is accomplished with ice packs and topical anesthetics, hydrocortisone cream, and/or antihistamine cream.