Allergic reactions are common and can occur from many different types of exposures, including bee stings, eating peanuts or by touching a poison ivy plant. Additionally, the adverse symptoms an individual develops can vary from a minor rash to a much more extreme anaphylactic life-threatening reaction. There are some exposures and reactions that many people, including myself as a physician, would not expect or anticipate.

Recently, I was the victim of such an unforeseen allergic exposure and serious reaction. When I felt a subtle burning sting on the back of my neck, I simply thought that the collar on my shirt was too tight. Despite the sensation continuing for some time, I failed to take notice of the cause until I reached back several minutes later to adjust my shirt once again. To my surprise, I saw a large and hairy caterpillar fall to the ground.

Within minutes, I began to develop a rash accompanied with a severe itch. At first, I thought it was psychological (it isn’t every day you find a hairy insect crawling on your neck); however, as the evening went on, the burning and irritation became more severe. Given my discomfort and the noticeable red blotches all over my body, I decided to research this creepy crawler. Amazingly, I learned that I had been “embedded” by the prongs of the black and white furry caterpillar.

The black and white furry caterpillar, also known as the Lophocampa caryae, is actually the larval form of the hickory tussock moth. Originally found in Canada, these insects have made their way south into the New England and Mid-Atlantic regions. Appearing most commonly during the summer and early fall months, the insect can be found eating the leaves of several tree and plant species.

These caterpillars have a unique defense mechanism in their fuzzy white and black hairs which when touched can release a venom. These hair-like follicles are actually “barbs” which inject a chemical into the skin, causing unpleasant adverse reactions. In some cases, the reaction is very mild, with no more than an irritation around the area where these hair follicles were embedded. However, in some cases, a more severe reaction can occur. Symptoms may include a diffused itchy rash, shortness of breath, headaches and nausea. Although extremely rare, the allergic reaction can even be life-threatening.

Although the literature suggests a very mild reaction is most common, in my case, I was extremely sensitive to the toxin and suffered a severe reaction. Despite treatment with topical creams, oral steroids and antihistamines, the severe symptoms lasted for over a week. What was even more intriguing is most of my physician colleagues I spoke with had never heard of this reaction.

If you see one of these critters, it is best to just leave them alone. Do not touch or handle them without gloves. Make sure your children don’t decide to play with one. Should you or your family member accidentally become exposed, quickly clean the area with soap and water in order to remove the barbs. Do not touch your eyes after handling them, as this can cause severe swelling. If a rash occurs, you can apply topical ointments such as steroids and antihistamines, as well as calamine lotion. Oral anti-histamines can help as well. However, should you develop a more severe reaction, contact your doctor immediately or dial 911.

Dr. Michael Schwartz is board certified in internal medicine and is affiliated with Soundview Medical Associates with a private practice in Darien. Visit his website at drmichaelbschwartz.com.