Outsmarting Poison Ivy


By Mary Carpenter

MYTHS ABOUND on the topic of poison ivy—from ways to protect yourself ahead of time, to what to do immediately after exposure and how to treat the rash—with each person swearing by different potions and solutions. But for the most important issue, how to stop the unbearable itch, one often-recommended remedy sure to be unsuccessful is Benadryl—because the immune system response it affects is unrelated to poison ivy.

(While drowsiness caused by Benedryl can offer some relief, Adnan Muhsen writes on Health.usnews.com, “I always warn people that you are just as likely to itch while sleeping as you are awake.” In addition, the rise in body temperature that can occur when asleep—as with warm showers and warm weather—can make the itching worse.)

Exposure to urushiol (oo-roo-shee-awl) oil from any of the PIOS—poison ivy/oak and sumac— plants causes a hypersensitivity reaction, mediated by T-lymphocyte cells—not the histamine response blocked by antihistamines like Benadryl, according to Wildlife Medicine magazine. From 50 to 75% of the US population is “sensitized” to PIOS plants—on the West Coast, referred to as getting “poison oaked.”  PIOS plants have widespread distribution throughout the US, and all three occur in mid-Atlantic states including the DMV.

To prevent the rash—called allergic contact dermatitis or Toxicodendron dermatitis, because all PIOS plants are in the Toxicodendron genus—the best approach is to avoid exposure entirely. Again from Wildlife Medicine: “Typically, urushiol is released from damaged PIOS plants and can unknowingly get on a person’s skin, clothes, or a pet’s fur resulting in primary or secondary exposure.”

For covering the body, gloves made of leather or heavy duty vinyl (PVC) will prevent urushiol penetration, as will clothes made of woven fabric such as wool. Other clothing should be disposable or washable. But the biggest challenge is the face —especially in typically hot poison ivy weather—for anyone removing poison ivy vines.

Urushiol oil typically becomes airborne only when the plants are burned—but pulling down the vines can release small amounts of oil into the air, where it can remain just long enough for people to become exposed. A Wilderness Medicine chart —two columns showing “time of washing after exposure” and “extent of removal of poison ivy oil”—indicates 50% removal if washing 10 minutes after exposure; 25% removal after 15 minutes; and “none” for those washing 60 minutes later or longer.

After any possible contact, wash everything involved—including gloves and tools— especially the body, but that’s where disagreement begins. Wildlife Medicine Magazine advises that the most effective cleansing comes from “repetitive high-pressure, single-direction gentle washing with dish soap (e.g. Dial Ultra or Dawn) under hot running water.” When unavailable, as in an outdoor setting, the recommended product is rubbing alcohol, either the liquid in small portable bottle or alcohol wipes.

Good old reliable Fels Naptha soap (yep, the same thing your grandmother used to wash her clothes)…does well,” according to Lancaster (PA)Pediatric Associates. After a rash develops, it “is not contagious (not even the draining blisters), but [the skin] typically has some remnant sap on it, so scratching will move the sap to a new place and cause it to spread.”

Different specialized poison ivy products have their advocates, most commonly supporting Technu for use as a wash, but also for application on dry skin “within eight hours of exposure,” reports Climbing. But according to Wilderness Medicine’s evidence, for reducing risk of a rash, Technu “is not significantly more effective than Dial Ultra dish soap and water.”

A popular if pricier alternative, Zanfel has gained a reputation as both a wash and a treatment. Says DMV-based landscape architect G.L., “Zanfel is especially effective in a way that no other treatment is…and that is when you apply it to a full-blown case. You can have bad itchy pustules and Zanfel will resolve them.” Zanfel may also work as a pre-exposure protector.

Effective barrier creams would be the optimal approach—and have been explored for years. But the only research-supported barrier cream to date is Ivy Block, discontinued in 2018 due to problems with preservatives. While a currently available option, Ivy-X, “claims to be effective, [there are] no published randomized clinical trials reporting effectiveness at this time,” according to Wildlife Medicine—though that may mean only that no one has done the research.

To deal with the rash, people swear by a huge range of solutions—from cold compresses and oatmeal baths to steroid creams and medications, notably prednisone. Some of these aim to reduce swelling, while others dry the fluid released from blisters—which can irritate the skin enough to cause more itching.

In my childhood, not far from Lancaster, Pennsylvania, I had terrible bouts of poison ivy every spring, followed by a few decades with no problem. Now that I have a garden, despite my best efforts and using many potions on the market, I am back to having a bad case every year that wakes me up at night. Either because I spread the oil in my sleep, or from airborne urushiol when removing the vines, the rash inevitably moves to my face—after which my doctor strongly recommends prednisone.

—Mary Carpenter regularly reports on topical subjects in health and medicine.

2 thoughts on “Outsmarting Poison Ivy

  1. Alan says:

    Another great article by Mary on a common health issue this time of year. My combat encounters with the enemy- poison ivy etc- teach that avoidance is hard, especially if you’re not paying attention as you weed in overgrown areas. And covering up is harder in our hot and humid climate. But if you’re afflicted, there’s one reliable relief that works for me- apply a stream of very hot water to all the areas with rash, so hot you can barely stand it. In return, you’ll get 4-8 hours of total relief from itching, and a bonus of less future itching in general. Then when itching starts again, repeat. Some have written not to do this because it might damage the skin, but I’ve been doing it for decades to get relief and a good night’s sleep, something no topical lotion offers.

    1. Janet Kelly says:

      I haven’t gotten poison ivy in ages, but I do see something very suspicious sticking out from my expanse of plain old ivy and will have to destroy it!
      In the meantime, Mary is out of town but I’m sure she’ll respond to your remedy for itch relief!

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