September 13, 2021

Can a Caterpillar Really Cause a Skin Rash?

The short answer on caterpillar stings from an emergency medicine physician

caterpillar on leaf

Q: You picked up a caterpillar on a hike and now your arm is an itchy patchwork of red bumps. Is that normal?

A: Don’t be fooled by the cuteness of a fuzzy caterpillar inching through the world in its adorable way. Some of those little critters pack a nasty punch that can leave your skin red, swollen and itchy.


Cleveland Clinic is a non-profit academic medical center. Advertising on our site helps support our mission. We do not endorse non-Cleveland Clinic products or services. Policy

The reason? It’s those tufts of bristly hair that make caterpillars look like a living stuffed animal — ironically, the whole reason why you picked the creature up in the first place.

The spike-like hairs in a few dozen caterpillar species are actually quills connected to poisonous sacs. Touch these hairs and they may break off in your skin, releasing a tiny dose of toxin in the process.

It’s basically a defense mechanism the caterpillar deploys to avoid being… well, manhandled by much larger creatures. (In this case, you.)

Symptoms of a caterpillar sting

Now the good news: Reactions to caterpillar stings usually stay on the mild side. On the scale of insect bites, it normally rates as more troublesome than a mosquito bite but not as bad as a wasp sting.

Your body’s response to the venom leads to a caterpillar rash and skin conditions that can last anywhere from a few hours to a few days. Symptoms could include:

  • Redness.
  • Itching.
  • Swelling.
  • Welts.
  • Blisters.

A more serious allergic reaction — including shortness of breath and difficulty swallowing — could develop if you touch your eyes or mouth after handling a caterpillar. There have even been rare reports of anaphylactic reactions.

First aid for caterpillar rash

So what’s your first move following the OUCH moment? (After expressing regret for not leaving the darn caterpillar alone, of course?) Let’s walk through some basic at-home treatment steps to offer relief.

  • Remove the toxin-laden hairs from your skin. This is best done by using adhesive tape. Gently put the sticky side against your skin on the affected area and lift up, which should pull the hairs out.
  • Wash the skin thoroughly with soap and water.
  • Apply an ice pack to reduce swelling and pain.
  • Create a paste using baking soda and water and slather it on the affected skin to reduce itching. A hydrocortisone cream also may be used.
  • Take an oral antihistamine (such as Benadryl®) if the reaction to the sting worsens.

If symptoms escalate despite these steps — think extreme swelling or difficulty breathing — visit a healthcare provider or urgent care center to be safe.

Best defense against stinging caterpillars

Nature often color codes dangerous creatures, painting them with bright hues that stand out as a warning sign to others in the ecosystem.

When it comes to fuzzy caterpillars, however, those markings often signal something else to people: Pick it up and check it out. That curiosity can come with a cost, as dozens of cool-looking stinging caterpillars reside in the United States.


The pain-inducing roster includes the:

  • Hickory tussock moth caterpillar.
  • Saddleback moth caterpillar.
  • Buck moth caterpillar.
  • Flannel moth caterpillars, including the puss caterpillar.

Now it’s true that the vast majority of caterpillars are harmless. (Here’s looking at you, Mr. Woolly Bear.) The best rule to follow? Admire caterpillars with your eyes and keep your hands to yourself.

Emergency medicine physician James Roach, DO

Related Articles

Female swimmer in the water at edge of a pool
December 1, 2023
Can Exercise Reduce Your Risk of Breast Cancer?

Physical activity and weight management can minimize your chances of getting the disease

Two people standing in the cold.
November 29, 2023
10 Colds Not To Catch This Winter

The flu, RSV, COVID-19, pneumonia and more typically circulate during cold weather months

Parent breastfeeding baby on bed, against the headboard.
November 27, 2023
Looking for Foods To Increase Your Milk Supply? Think Big Picture

No single food will increase your milk, but an overall healthy diet will help

Parent uses manual baby aspirator to open up nasal passages of baby.
November 22, 2023
Prevent Phlegm in Your Baby’s Throat With a Nasal Aspirator

Keeping your baby’s airways clear of mucus helps with breathing and feeding

Two different vaccines and needles displayed in foreground.
November 22, 2023
Which Vaccines Can You Get at the Same Time?

Getting routine vaccinations together can save you time and may be more effective

Muffins and sweetbreads with frosting on trays at bakery.
November 22, 2023
13 Foods That You Didn’t Know Contain Dairy

Be sure to check the labels of common foods like canned tuna, bread, hot dogs and chocolate

Toddler drinking from a cup while at the table during dinner.
November 21, 2023
Toddler Drinks — What Does the Research Say About These Products?

They aren’t unhealthy, but they’re probably a waste of money

person drinking coffee at computer at night
November 15, 2023
Is It Bad To Drink Coffee Late at Night?

Depending on your sensitivity to caffeine, a late-night cup may be just fine

Trending Topics

group of hands holding different beverages
November 14, 2023
10 Myths About Drinking Alcohol You Should Stop Repeating

Coffee won’t cure a hangover and you definitely shouldn’t mix your cocktail with an energy drink

Person applies moisturizer as part of their skin care routine after a shower.
November 10, 2023
Korean Skin Care Routines: What You Need To Know

Focus on the philosophy — replenishing and respecting your skin — not necessarily the steps

glass of cherry juice with cherries on table
November 8, 2023
Sleepy Girl Mocktail: What’s in It and Does It Really Make You Sleep Better?

This social media sleep hack with tart cherry juice and magnesium could be worth a try