Caterpillar rash, or lepidopterism, occurs when contact with caterpillars causes skin irritation. Treatment includes using ice packs, corticosteroid creams, and antihistamines.

Lepidoptera is the classification that includes moths and butterflies and, therefore, caterpillars. There are approximately 165,000 different species. While most species are completely harmless to humans, some types of caterpillars can cause adverse reactions.

Research indicates that 150 species within Lepidoptera can affect humans, including 50 species in the United States. Lepidopterism is when contact with a harmful caterpillar causes an allergic reaction that may affect the skin and other systems in the body.

Caterpillar rash can affect the skin differently, but it can cause pain and hives in the affected area.

This article discusses the ways to treat caterpillar rash, prevention, and when to contact a doctor.

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Treatment for caterpillar rash includes minimizing further reaction by removing as many venomous caterpillar hairs from the skin as possible and using ways to relieve the symptoms of the reaction. This includes using:

Researchers note that nonsteroidal anti-inflammatory drugs (NSAIDs) are not generally effective as pain relief for caterpillar rash.

A person may use local cooling measures, such as applying an ice pack or topical isopropyl alcohol on the affected area. This may reduce any swelling and relieve pain.

Both an ice pack and topical isopropyl alcohol can cause stinging, but a person may avoid this by applying them gently. Wrapping an ice pack in a towel or cloth reduces harshness on the skin.

While local cooling measures may provide pain relief, using them for long periods can adversely affect an area of skin.

Corticosteroid creams are over-the-counter (OTC) medications that people usually use to treat skin conditions such as eczema. They may be useful for treating caterpillar rash.

A person can manage symptoms by applying corticosteroid creams to the skin, which may reduce the rash in the short term.

However, using corticosteroid creams for long periods can have adverse effects on the skin. A person should only use this medication as directed by a healthcare professional.

Side effects of corticosteroid creams can include:

This type of medication is particularly helpful for treating itchy skin.

Second-generation antihistamines cause fewer side effects than other types of antihistamines. This is because they do not cross the blood-brain barrier, which leads to the central nervous system. Adverse effects are not common but may include:

People should ensure to take antihistamines as directed by a healthcare professional.

An important aspect of treatment is to prevent symptoms from worsening by removing any possible remains of the caterpillar’s venom. A person can wash the affected area with baking soda to help reduce symptoms while reducing the risk of further allergic reactions.

Using baking soda to bathe the rash may reduce inflammation and pain or burning sensation. It may also remove any remains of venom from caterpillar spines or hairs that are still penetrating the skin.

A person can also use soapy water to help remove remaining traces of caterpillar venom. It is best to remove any visible caterpillar hairs or spines from the skin using adhesive tape or forceps.

A person may learn how to identify which caterpillars can cause harm, but the best way to prevent caterpillar rash is to assume all species are toxic and avoid contact with any of them.

People may also learn when peak caterpillar season is in their local area. This makes it easier to know when to be particularly alert for them. During peak caterpillar season, a person should wear protective clothing, such as long sleeves and pants, to cover up as much skin as possible.

If there is a significantly heavy caterpillar infestation in an area, people should wear full personal protective equipment, including eye protection and a respirator mask.

A person should consult a doctor as soon as possible if a sting causes severe pain. Treating a sting early and efficiently can restrict symptoms from progressing to a more severe condition.

Severe allergic reactions are rare, but studies indicate that they may occur following exposure to caterpillar venom. Allergy symptoms for people to be aware of include:

Most Lepidoptera species are completely harmless, and contact with butterflies and moths does not cause adverse effects. However, contact with some species of caterpillars can cause a skin reaction that people may refer to as caterpillar rash.

Treatments involve home remedies, such as applying an ice pack or washing the area with baking soda. Other treatments include OTC medications such as corticosteroid creams or second-generation antihistamines.

However, if someone is experiencing a particularly severe reaction, they should contact a doctor as soon as possible.