How to Spot and Treat a Caterpillar Rash

A rash from a caterpillar, also called lepidopterism, occurs when the tiny hairs on a caterpillar touch the skin and cause a rash.

It's true that an encounter with a caterpillar isn't as dangerous as, say, a bee sting or a tick bite can be. But caterpillars can cause a red, itchy, swollen, and even painful rash. Treatment for caterpillar rash may include ice packs, antihistamines, steroid cream, and more.

Here's what to know about how to recognize a rash from a caterpillar, what symptoms you may experience, and how to treat it.

Caterpillar Rash Causes and Symptoms

The fuzzy tufts on caterpillars are what can cause a rash. These tiny hairs are called setae. In some people, these hairs cause an allergic reaction when they touch the skin.

This immune response occurs when the body sees a substance as a threat even if it's not. The immune system will flood the body with a chemical called histamine. Touching a caterpillar can trigger this release of histamine, causing symptoms such as:

• Redness
• Swelling
• Itching
• Rash
• Welts
• Vesicles (small, fluid-filled sacs)
• Burning or stinging sensation

These symptoms can appear within minutes and last for one or more days.

If you touch your eyes or nose after handling a caterpillar (or if a child places one in their mouth), there could be a more serious reaction. Symptoms might include

• Sneezing
• Coughing
• Runny nose
• Red eyes
• Shortness of breath
• Mouth pain
• Itching
• Difficulty swallowing

If you notice any of these symptoms, go to your nearest urgent care center or emergency room.

It is extremely unlikely that caterpillar setae could cause anaphylaxis, a full-body, sometimes life-threatening reaction, but it has been seen occasionally after exposure to certain caterpillars. Seek immediate emergency care with symptoms such as:

• Hives
• Significant swelling of the tongue or lips
• Difficulty breathing or swallowing
• Nausea, vomiting, or diarrhea
• Headache, sweating, or dizziness

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Diagnosis

There are no tests to make a diagnosis, so a healthcare provider will perform a physical exam and ask about your symptoms.

Rashes from caterpillars can easily be mistaken for something else, and therefore not treated properly. In 2011, 23 children in Florida developed rashes from exposure to white-marked tussock moth caterpillars (Orgyia leucostigma).

According to the report issued by the Centers for Disease Control and Prevention (CDC), most of the kids were diagnosed with other conditions at first. These included chickenpox, molluscum contagiosum, and even potentially life-threatening MRSA infections.

In other cases, rashes caused by caterpillars have been mistaken for:

• Contact dermatitis
• Atopic dermatitis
• Phytophotodermatitis
• Scabies
• Scarlet fever
• Fifth disease (parvovirus B19)
• Flea bites or mosquito bites

One of the recommendations by the CDC in response to the Florida outbreak was to advise schools and daycare centers where caterpillars are common to power wash playground equipment to remove the caterpillars.

How Do You Treat a Caterpillar Rash?

If a rash develops after an encounter with a caterpillar, it usually won't be serious and can be treated at home. If the reaction is mild, you will first need to remove any of the tiny caterpillar hairs on the skin.

To do this, place a strip of tape on the area of the skin with the hairs. The hairs will stick to the tape when you pull it off. This works the way a lint roller does (and you can actually use one of those if you have one). Repeat with fresh pieces of tape until you've removed most or all of the caterpillar hairs.

Then, wash the skin with soap and water and use any additional treatment options, such as:

• Ice pack applied to the area for 10 to 15 minutes
• Baking soda mixed with a small amount of water to make a paste
• Over-the-counter non-drowsy oral antihistamine (such as Zyrtec or Clarinex)
• Over-the-counter corticosteroid creams

How to Prevent Caterpillar Rash

There are several ways to prevent caterpillar rash, including:

• Avoid touching all caterpillars.
• Learn how to identify harmful types and avoid touching them.
• Find out where caterpillars are most common in your local area, when their in peak season, and then avoid the area during that time.
• Wear protective clothing, including a long-sleeved shirt, pants, long socks, and closed-toed shoes.

Summary

Rashes from a caterpillar are rarely serious, but they can be painful. If you do get a rash, it should go away quickly once the hairs are removed and you treat it with at-home and over-the-counter remedies. If you have a more serious reaction, call your healthcare provider or go to an urgent care center or emergency room.