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Outsmarting Poison Ivy

and Other Poisonous Plants

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First comes the itching, then a red rash, and then blisters. These symptoms of poison ivy, poison oak, and poison sumac can start from a few hours to several days after exposure to the plant oil found in the sap of these poisonous plants.

Not Contagious
Poison ivy and other poison plant rashes can’t be spread from person to person. But it is possible to pick up the rash from plant oil that may have stuck to clothing, pets, garden tools, and other items that have come in contact with these plants. The plant oil lingers (sometimes for years) on virtually any surface until it’s washed off with water or rubbing alcohol.

The rash will only occur where the plant oil has touched the skin, so a person with poison ivy can’t spread it on the body by scratching. It may seem like the rash is spreading if it appears over time instead of all at once. But this is either because the plant oil is absorbed at different rates in different parts of the body or because of repeated exposure to contaminated objects or plant oil trapped under the fingernails. Even if blisters break, the fluid in the blisters is not plant oil and cannot further spread the rash.

Tips for Prevention
Learn what poison ivy, oak, and sumac plants look like so you can avoid them. Wash your garden tools and gloves regularly. If you think you may be working around poison ivy, wear long sleeves, long pants tucked into boots, and gloves. Wash your pet if it may have brushed up against poison ivy, oak, or sumac. Use pet shampoo and water while wearing rubber gloves, such as dishwashing gloves. Most pets are not sensitive to poison ivy, but the oil can stick to their fur and cause a reaction in someone who pets them.

Don’t scratch the blisters. Bacteria from under your fingernails can get into the blisters and cause an infection.

Wash your skin in cool water as soon as possible if you come in contact with a poisonous plant. The sooner you cleanse the skin, the greater the chance that you can remove the plant oil or help prevent further spread. Use the topical product “Ivy Block” if you know you will come into contact with the poisonous plants. This FDA-approved product is available over the counter.

Tips for Treatment
Don’t scratch the blisters. Bacteria from under your fingernails can get into the blisters and cause an infection. The rash, blisters, and itch normally disappear in several weeks without any treatment. But you can relieve the itch by using wet compresses or soaking in cool water, applying over-the-counter topical corticosteroid preparations or taking prescription oral corticosteroids, and applying topical over-the-counter skin protectants (such as calamine) labeled to dry oozing and weeping or to relieve itching and irritation caused by poison ivy, poison oak, and poison sumac.

See a doctor if you have a temperature over 100° F; there is pus, soft yellow scabs, or tenderness on the rash; the itching gets worse or keeps you awake at night; the rash spreads to your eyes, mouth, genital area, or covers more than one-fourth of your skin area; or the rash is not improving within a few days.


Source: U.S. Food and Drug Administration,

This article was originally published in Coping® with Allergies & Asthma magazine, Spring/Summer 2009.