Caterpillar Envenomation Treatment & Management

Updated: Jul 18, 2022
  • Author: Andrew G Park, DO, MPH, FAWM; Chief Editor: Joe Alcock, MD, MS  more...
  • Print

Prehospital Care

The involved skin should be immediately washed with soap and water, and dried without contacting the skin (eg, use a hair dryer).

Local cooling measures can be applied to reduce pain. This may be enhanced by applying topical isopropyl alcohol or ammonia.

Following ocular exposure, the eyes should be irrigated immediately with copious water.

Following dermal exposure to irritant or toxic hairs or setae of caterpillars or moths, sticky tape (especially duct tape) can be applied to the site in an effort to remove retained setae. Occasionally forceps or tweezers may be required. Alternative effective methods of removal include use of rubber cement, clear fingernail polish, or facial peels (each applied, allowed to dry, then peeled away).

If acute symptoms follow respiratory exposure, supportive care is in order as necessary, including oxygen, antihistamines, and beta-agonist inhalers, if available.

Anaphylaxis should be treated in standard fashion.

Any potentially constrictive jewelry should be removed before swelling progresses in order to reduce risk to the distal limb or joint.


Emergency Department Care

Wash the skin with soap and water as mentioned above if this has not already been done in the field.

Ensure appropriate tetanus immunization status.

Skin exposure

Apply sticky adhesive tape (especially duct tape) to the site to remove all remaining hairs or spines possible. Other measures of removal as described previously for prehospital care can also be tried.

Acute dermatitis can be treated with antihistamines (H1 and/or H2 blockers), although their efficacy is controversial. Additionally, topical steroids may be employed. Systemic steroids may be necessary in patients with severe or persistent cutaneous symptoms. Application of antipruritic products containing menthol may be soothing.

Prostaglandin-synthetase inhibitors, such as aspirin or indomethacin, have been reported to reduce associated discomfort, but should be avoided if any evidence of coagulopathy is present.

Respiratory exposure

Symptoms can be managed with antihistamines (H1 and/or H2 blockers) and beta agonist aerosols/inhalers if wheezing is present.

If significant symptoms occur, supplemental oxygen administration may be needed, and systemic steroids may be useful.

Ocular exposure

Instill a topical anesthetic and irrigate the eyes immediately with copious saline. A Morgan lens can facilitate this.

Perform a slit lamp examination with fluorescein and Woods lamp for concern of possible abrasion. The patient should receive close ophthalmologic follow-up to rule out retained setae or hairs.

Eye complications resulting from retained migrating hairs/setae can be severe, and surgical excision may be necessary.


Management is primarily supportive with symptom management. Splint and elevate the involved extremity; ice can be applied to reduce pain and swelling. Efforts, as outlined above, should be instituted to remove any retained spines or hairs. In general, pain from these stings often improves and resolves within hours.

Narcotic analgesics may be required for pain relief. Anecdotal reports exist of the successful use of calcium gluconate (eg, 10 mL of a 10% solution by slow intravenous [IV] administration) to relieve muscle pain following M opercularis stings. Antihistamines (H1 and/or H2 blockers) may reduce concomitant pruritus.


Treat rare cases of caterpillar or moth-related anaphylaxis in standard, aggressive fashion, including airway management, epinephrine, oxygen, antihistamines, steroids, IV fluids, and vasopressors as needed.



All caterpillars should be considered potentially toxic, and contact should be avoided. Children particularly should be warned in this regard. When working outdoors during peak caterpillar seasons, individuals should wear long-sleeved shirts, long pants with the cuffs tucked into their socks, and work gloves. Collars should be close fitting to avoid having a caterpillar fall into one's shirt. A broad-brimmed hat may prevent caterpillars from falling from an overhead tree onto one's head and face. When working in an area where airborne caterpillar debris is a problem, a tight-fitting face mask and eye protection should be used. Laundered clothing should not be hung outdoors to dry as it may collect airborne caterpillar debris.

Insecticides can be used to control caterpillar populations. A professional pest specialist or entomologist should be consulted before applying such agents because many caterpillar species are beneficial to agricultural and ornamental plants.

If a caterpillar is found on one's body, it should be gently lifted off with a stick to avoid contact with potentially toxic hairs, setae, or hemolymph.


Long-Term Monitoring

Victims of caterpillar stings can be observed for 2 hours in the ED to ensure that they do not develop significant systemic toxicity.

Although uncommon, secondary infection can occur following erucism or lepidopterism. Instruct patients to follow up immediately if any signs or symptoms of infection occur. Patients with particularly severe exposures should have scheduled follow-up care to exclude infection or necrosis.

All patients with ocular exposures to caterpillar or moth hairs or setae should receive early ophthalmologic follow-up care to exclude retained fragments, which can lead to catastrophic complications.

Following caterpillar stings, local findings, including pain, may persist for several days. Systemic symptoms usually resolve in 24 hours.

Patients who experience a significant allergic reaction to caterpillar exposure (eg, hypotension, bronchospasm) should receive a prescription for an epinephrine self-administration device prior to discharge from the hospital and should be instructed in its use. They also should consider obtaining and carrying medical alert identification of this history. Unlike therapy for hymenoptera-induced anaphylaxis, there is no desensitization therapy for patients highly allergic to caterpillars.