Poison Ivy: Scratching The Surface You're never too old to develop an allergic sensitivity to poison ivy, oak, or sumac. But taking a few precautions can help minimize the nastiness of the encounter.
NPR logo Poison Ivy: Scratching The Surface

Poison Ivy: Scratching The Surface

Pill Proves Elusive

Generations of doctors have tried to find a way to reverse sensitivity to poison ivy, poison oak and sumac.

At least 85 percent of people will eventually become allergic to poison ivy after a run-in with the vine or its itchy relatives, poison oak and sumac. If you haven't been hit with the rash yet, just wait. You're never too old. But a few precautions can help minimize the nastiness of the encounter.

If I "let leaves of three be," will I be able to steer clear of the itchy plants?

No, though that's a good start. The leaflets of poison ivy, oak and sumac usually grow in triplets extending from a single stem, but you'll sometimes see leaf clusters of five or seven or more. All three plants are masters of disguise — now green, then red, sometimes shiny, sometimes fuzzy. They can look like vines, shrubs, even trees. Best to study the variations.

What are the symptoms?

Intensely itchy rash-red bumps and blisters that often form a streak where the plant scraped the skin.

I've had that rash, but I swear I never touched a plant. What happened?

People have developed rashes from mowing the lawn, unloading firewood, walking barefoot on mulch, petting a dog or picking up gardening gloves a year after they were contaminated. The problem is the urushiol resin in the sap of poison ivy and oak (also found in mango rinds, cashew shells, and certain Japanese lacquers). Urushiol is sticky and tenaciously potent.

I've never had a plant allergy. Am I immune?

Unlikely. Studies suggest almost anyone would develop an allergy to urushiol if exposed to a big enough dose. Your general health, genetics and other unknown factors may also play a role in how sensitive you become to the oil.

I touched it. What now?

Experts say most people who are sensitive have at least 10 or 15 minutes to remove the sap and avoid the allergic response, which doesn't start until the oil penetrates lower layers of skin and binds to cells there. After exposure, rinse with rubbing alcohol or use wipes if handy, or flush the area with running water. As soon as possible, lather the affected skin a few times with a mild detergent soap (fatty soaps risk spreading the oil; showers are better than baths for the same reason). Contaminated clothes should be carefully removed, bagged and laundered alone in soapy water.

Too late. It's been a couple of days, and I'm itching and blistering. What now?

There are several relatively expensive soap pastes sold in outdoor stores that claim they can squelch — or at least shorten —your misery even after blisters form. The makers of at least one such soap, Zanfel, have presented findings at a scientific meeting that seem to back their claims. But that research hasn't yet been published in an independent journal.

Does anything else bring relief?

Experts say lots of things may be worth trying, starting with cool compresses. The rash could last a few weeks. Colloidal oatmeal baths and calamine lotion are traditional nontoxic, anti-itching salves. Antihistamine pills may help you sleep, but ointments containing antihistamines won't help; corticosteroid salves may, if applied when the itching starts. If the rash is extensive, your doctor may prescribe a short course of oral steroids.

Isn't there some sort of protective lotion to put on before I go out?

Several barrier creams are sold at drugstores, but only one type, IvyBlock, has been evaluated by the Food and Drug Administration as safe and effective. It contains bentoquatum, a finely emulsified clay that's been found to absorb urushiol before it can penetrate the skin. The lotion must be reapplied every four hours to be effective.