Itchy caterpillars: symptoms, diagnosis and treatment

Symptoms

Symptoms from stinging caterpillars usually include instant pain, with a longer lasting ache and a raised weal that usually soon subsides. 

Contact with the venomous or irritating hairs include symptoms of extreme itch followed by wheals and a variable rash which can include a burning sensation. Other symptoms are dermatitis, pain, itching, and swelling of the affected area. 

The intensity of the irritation is dependent on the sensitivity of the patient and the species of caterpillar.

Detached hairs if inhaled may cause laboured breathing. Irritation in some cases can last for days. Eye injuries have also been reported and may lead to conjunctivitis.

Diagnosis

A recent history of contact with a moth, caterpillar or food plants are usually required to determine if and which caterpillar has caused a problem. Identification of the caterpillar or moth with pictures or taxonomic keys is essential in the prevention and control of stinging and itchy caterpillar infestations. 

Medical Entomology staff can identify the moths or caterpillars and offer advice on control and avoidance.

Treatment and control

Avoid contact with any hairy caterpillars or materials that they have contacted. When handling these insects, suitable protective clothing such as eyewear and gloves should always be worn. Most infestations are short lived and will subside after a short period. 

If the caterpillar infestations are causing an appreciable problem, a pest control officer can chemically treat the food plant or harbourage area. Infestations will normally die out through the depletion of food resources or predation.

Treatment of affected skin by itchy caterpillars includes the removal of all affected clothing. Apply a piece of adhesive tape to the affected areas and pull the tape off immediately. This should remove the majority of the hairs and reduce the irritation. The tape can be examined under the microscope to observe hairs.

Wash all areas where itchy caterpillars have been observed or where irritation occurs. Commonly irritation occurs from touching the caterpillar or moth, or contact with bed linen after moths or airborne irritating hairs have landed on washing. 

Stinging caterpillars are usually only on the food plants and direct contact with the caterpillar causes the sting. The best remedy is to recognise the food plants and avoid them at their active growing period.

Ice packs, analgesics, creams, antihistamines and lotions with steroids may assist in relieving the symptoms of both types of reactions.

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Last updated: 27 June 2017