This article appears in Summer Home & Garden 2018.

Up to 85 percent of people are allergic to poison oak, ivy or sumac, according to the American Skin Association, but you can take the itch out of summer with a few helpful tips.

What to know

— These poisonous plants grow everywhere in the United States except Hawaii, Alaska and some desert locations in Nevada.

— Identification isn’t as easy as “if you see leaves of three, let them be”: Poison ivy typically grows in the form of a vine often along riverbanks. Poison ivy’s less-common cousin, poison oak, can be identified by leaves that look like hairy oak fronds.

— Poison ivy carries an irritant oil called urushiol that can be released if plants are touched, broken or burned, said Dr. Claire Hollins, a dermatologist with Penn State Health Milton S. Hershey Medical Center. While some people are not sensitive to urushiol, others develop a red, itchy or painful rash, swelling or blisters where the irritant comes in contact with the skin. The reaction typically takes at least 24 hours to develop, happening faster each time you are exposed.

— Many people don’t know that poison ivy and poison oak can also become airborne and be spread by burning piles of wood or brush that includes the leaves, Hollins said. “Sometimes people wake up days later and their eyes are puffy and swelled up so much that they can’t see but they don’t know why,” Hollins said. It’s also possible for people to chop firewood in the summer, and the urushiol oil from poison ivy on it is reactivated by burning that wood in the winter months, she said.

— The best prevention is to avoid contact with poison ivy altogether: When in nature wear long pants and sleeves, socks and gardening gloves.

How to treat

If you think you may have come into contact with a poisonous plant, wash your hands immediately with warm, soapy water and dry them on a disposable towel rather than cloth towel to avoid spreading the harmful oils. Avoid vigorously scrubbing the area or using hot water because these may further open pores or cause more irritation to the skin.

If irritation develops, it can be treated with over-the-counter hydrocortisone ointments. More serious cases may require a course of oral prednisone and stronger topical steroids from a dermatologist or primary care provider.

Cool baths or compresses can offer relief. Massage the affected area with an ice cube and let the area air dry. Allowing it to air dry will reduce itching and oozing of blisters.

Poison ivy is not typically passed from one person to another unless the oil is still present on clothing or skin, Hollis said. It is also not spread by scratching areas that itch, as the urushiol is not present in blister fluid.

Hershey Medical Center’s Department of Dermatology is conducting research to look for a vaccine for poison ivy, and researchers are currently testing an urushiol patch to see how effective it is.