Healthy Living

Poison Ivy: Prevention Takes Priority

Jun. 16, 2017

Before heading out to dig in your garden, take steps to avoid a poison ivy encounter that might make you miserable. UR Medicine dermatologist Dr. Mary Gail Mercurio tells you what to look for and offers steps to take if poison ivy finds you before you find it.

poison ivy plant

Poison ivy, a toxic vine formally known as toxicodendron radicans, is the cause of a common—and often miserable—allergic skin reaction. Poison ivy is widespread in our region and its characteristic cluster of three almond-shaped leaves is familiar to many as is the adage: Leaves of three, let them be.

When exposed to the plant, people who are allergic can develop a red, itchy rash, sometimes with painful red bumps that often develop into fluid-filled blisters and tend to show up in lines or streaks corresponding with the areas of contact with the plant. The rash’s linear nature is one way to distinguish it from bug bites, also rampant in summertime. 

The precise culprit within poison ivy is uroshiol, its oily sap. More than 75 percent of people are allergic to poison ivy, and the rash can begin anywhere from a few hours to a few days after exposure to the plant. Even if you haven’t had a problem with poison ivy, with repeated exposure, it’s possible to develop an allergy over time.

picture of poison ivy rash

The rash itself is not contagious. By the time it appears, the oil has either been washed off or absorbed into the skin. Touching the blister fluid cannot spread the rash. However, when the invisible oil gets on the hands and then other body parts are touched before the hands are washed, it is possible to unknowingly spread the rash widely, including to areas that came nowhere near the plant. Similarly, it is possible to get the rash from touching the oil on another person’s skin, a pet’s fur, or objects like gardening gloves or shoes that touched the plant and then contacted your skin before being washed. All of this happens long before a rash appears. Whenever there is a question of having been in contact with poison ivy, it’s wise to wash immediately with soap and water, and do the same for any clothing or objects to stop the spread.    

These tips may help you avoid the perils of poison ivy this summer:

  • Know it when you see it. Learn to recognize the plant so you can avoid it.
  • Block it. Consider using a barrier cream, which may reduce the risk of the plant’s oil penetrating your skin, in the event you are exposed to it.
  • Stop it in its tracks. If you think you’ve been exposed, do your best to wash the oil off your skin. 
  • Soothe it. If a rash does develop, work to keep it in check with an anti-itch or corticosteroid cream.
  • Get to know its counterparts. A variety of plants can cause rashes similar to poison ivy. Before spending time in the woods or garden, do a little online detective work to familiarize yourself with other culprits so you can enjoy being outdoors without worrying.
  • Seek help if it’s severe. In some instances, a poison ivy rash can be widespread or severe, involving the mouth, eyes, genitals or—worst of all—inhaled in smoke from a fire containing the leaves. In these cases, systemic corticosteroids and even hospitalization may be necessary. 


Dermatologist Mary Gail Mercurio


Mary Gail Mercurio, M.D., is a professor of Dermatology and Obstetrics and Gynecology at URMC, caring for patients at UR Medicine’s Strong Memorial Hospital. She has special interest in skin and hair disorders in women.