Along with poison oak and sumac, poison ivy is responsible for the most common plant allergies in the United States. First published records of poison ivy dated in the 1600s; “Poison Ivy” was coined by Captain John Smith in 1609. One billionth of a gram (a nanogram) can cause a rash, but most people come into contact with about 100 nanograms! 500 people could itch from the amount covering the head of a pin

Specimens of urushiol oil hundreds of years old have caused dermatitis in sensitive people The oil normally stays active for 1 – 5 years on any surface. Its name is derived from urushi, a Japanese word meaning “lacquer.”


How can a few drops of oil spoil a great trip?

If it’s urushiol oil – oil secreted from the poison ivy plant – it’s pretty easy to figure out. In fact, you may be one of millions of people who found out the hard way that a poison ivy rash is one vacation souvenir you can live without! So before you pack up for your week in the Great Outdoors, check out this quick primer on how to spot poison ivy and deal with its effects.

How it spreads

Poison ivy is easy to avoid if you know what to evade. The problem is not the plant itself, but what’s inside the plant’s stems, leaves, berries, and roots.

When the delicate leaves of the poison ivy plant are damaged by contact from people, insects or animals, it exudes urushiol oil (pronounced “oo-roo-shee-ohl”).

Once this oil contacts the skin of a sensitive individual, it rapidly penetrates the outer layer of dry skin (the epidermis) and gets into the living layer (the dermis) where the allergic reaction occurs.

It doesn’t take much oil to make you miserable. If you barely brush your skin against the plant, a rash of red pimples, even blisters, can break out. Physicians term this reaction “contact dermatitis.” In response to the irritating oil, the body produces histamines, the substance that causes an overabundance of mucous when you have a cold. In the case of a poison ivy rash, the fluid shows up as blisters in the skin. (Note: The fluid is not the oil, rather the body’s attempt to wash it away.)

Unfortunately, the oil is very transferable. You don’t have to come into direct contact: touching your skin against clothing, pets, or even inanimate objects on which the oil has transferred can cause a reaction. See Poison Ivy Facts and Myths for more information on how it’s spread.

Stopping poison ivy before it stops you

You know you don’t want to get too close to poison ivy. But how do you avoid it when you’re hiking, fishing, camping, and doing all the other things you love to do in the woods? Knowing the plant’s appearance and habitat is your greatest protection.

Unfortunately, poison ivy is an adaptable plant that may appear as little sprouts, vines, or bushes with shiny green or dull green/brown leaves. Seeing one plant is an indication that more will be in the area-usually in a proverbial “patch” characterized by marginal soil and drainage.

The good news is that all varieties share a common trait: poison ivy leaves grow in clusters of three, with two leaves growing opposite on the stem and the third at the top. Just be aware of your surroundings and steer clear of anything resembling poison ivy.

Sounds simple enough, but just knowing the plant’s appearance won’t be enough if you’re traveling through areas rife with poison ivy. You’ll have to “dress defensively” by wearing clothing that minimizes your skin’s exposure to poison ivy plants. Long pants, long-sleeved shirts, and hiking boots will help, as will gloves. Coincidentally, the same type of clothing worn to prevent poison ivy will also help protect you from ticks, which in some cases can cause Lyme disease.

You’ll also find some creams on the market which are designed to protect you from poison ivy exposure. These products coat the epidermis with a substance that neutralizes the oil before it penetrates your skin. Consult your dermatologist for more information.


About one in 10 people experience an allergic reaction to poison ivy within a few hours, Unfortunately, when blisters appear, that means the deep dermis layer is affected. These symptoms can last from 3 to 10 weeks. Typical reactions, depending on the amount of exposure, include redness and swelling, rash, and blisters at the points of contact-but not on areas which have not been exposed to the oil.


Most experts recommend washing the affected area thoroughly to remove as much oil as possible. Lots of soap and water will work. Some claim that using rubbing alcohol (isopropyl) on exposed areas first removes more oil. If you wash with rubbing alcohol, keep in mind that your skin’s natural protection from nature’s nasty things will be temporarily gone-so you might not want to go back out to the same area again because of the risk of a second contact with poison ivy.

It pays to treat all clothing that may have been infected as hazardous waste. Seal all articles in plastic bags until you can put them in the washing machine. Don’t forget to wash everything that may have come into contact with poison ivy, including hats, jackets, shoes, camping accessories, pets, chair legs, and balls. If you don’t, you may be in for a nasty surprise next hunting or fishing season, when you use touch these items later!

To ease itching, you can use calamine lotion, baking soda or oatmeal. For mild cases, wet compresses or soaking in cool water may be effective. Topical antihistamine products may also help. Over-the-counter topical corticosteroids (commonly called hydrocortisone under brand names such as Cortaid and Lanacort) may also provide relief from itching.

Multiple broken blisters, dark red lines in the skin radiating from a scratched rash area, or any reaction that may indicate a general allergic reaction deserves immediate, professional medical attention.