Fredericksburg Parent

14 Fredericksburg Parent and Family • March 2023 INTERVIEWED BY EMILY FREEHLING Ask the Expert a sk t h e e x p e rt "Leaves of three—let it be." So goes the old adage on how to recognize poison ivy. According to the American Skin Association, urushiol—the allergenic substance found in poison ivy, poison oak and poison sumac, causes the most common allergic reaction in the U.S., affecting up to 50 million people each year. The itchy skin rash caused by aller- genic substances is called contact dermatitis. As spring brings green shoots, it's good for parents to be prepared for contact dermatitis caused by plants or other allergens. As our March Expert, Dr. Jonathon Posthumus, M.D., a board-certified, fellowship trained allergist with Allergy Partners of Fredericksburg, answers questions about contact dermatitis in children and adults. Q: How can parents distinguish contact dermatitis from other kinds of allergic reactions, such as from foods? Dr. Posthumus: Allergic contact dermatitis presents as an itchy rash localized to the site of allergen contact with the skin. The configuration and location of the dermatitis often is a clue to the offending allergen. For example, areas of linear raised rashes on exposed skin after a hike in the woods or yard work is classic for poison ivy-induced contact der- matitis. It can take hours to days for a contact dermatitis rash to occur after contact with the offending allergen. Contact reactions, such as hives, from physical contact with the foods occur in the area where the food touched as well, but they occur immediately after contact, usually within minutes. Q: What are some of the most common causes of contact dermatitis? Dr. Posthumus: Contact allergens can be both natu- ral and man-made. The most common plant contact allergen is urushiol, found in plants such as poison ivy, poison oak, and poison sumac. Other common childhood contact allergens in the United States include metals, topical antimicrobials, fragrances, preservatives such as formaldehyde, and chemicals in skin and hair care products. Q: Are there any ways that these reactions differ in children versus adults? Dr. Posthumus: Manifestations of contact derma- titis are usually very similar in children and adults. Contact dermatitis can develop after years of tolerat- ing a product or metal, for example, so allergens tol- erated as a child can be troublesome as an adult. What's That Rash? A Parent's Guide to Contact Dermatitis Dr. Jonathan Posthumus, M.D.

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