What Is Poison Ivy? Symptoms, Causes, Diagnosis, Treatment, and Prevention

It’s wise to know how to identify poison ivy if you encounter it and how to get rid of it safely if it’s on your property.

If you have a mild reaction to poison ivy, you likely can treat it at home using over-the-counter (OTC) medicines or home remedies to relieve discomfort. But in severe cases, you should seek medical treatment.

A poison ivy skin rash can arise in as little as four hours if you’ve previously been exposed to the plant, or as long as three weeks if it’s your first exposure to it.

• Redness, often in streaks or lines
• Black spots or streaks
• Intense itching
• Blistering
• Swelling, especially if the reaction is serious

The severity of your reaction will depend on your natural level of sensitivity, as well as how much of the plant’s oil has bonded to your skin.

After about a week, your blisters will start to dry up, and the rash should begin to fade. More severe skin reactions, or those covering larger areas of your body, may take longer to clear up.

Poison ivy contains an oily resin known as urushiol. It’s colorless and odorless, and is found in the leaves, stems, and roots of the plant.

This oily substance easily sticks to many different types of surfaces when it comes into contact with them, including skin, clothing, pet fur, and outdoor tools and equipment.

“If you get it on your shoelace, then you tie your shoe and you wipe your forehead, you could have poison ivy on your forehead,” says Linda Radimecky, an interpretive naturalist at Afton State Park in Hastings, Minnesota.

No one is born allergic to poison ivy, though.

“Our bodies become sensitized to poison ivy after an initial exposure,” says Joshua Zeichner, MD, director of cosmetic and clinical research in dermatology at Mount Sinai Hospital in New York City. “Upon future exposure, our immune system becomes activated, leading to significant inflammation.”

In addition to direct contact and touching contaminated items, you can also have a poison ivy reaction by breathing smoke from the plant if it’s burned.

Poison ivy isn’t contagious unless there is still oil from the plant on your skin and you spread it to other surfaces. You also can’t spread a rash across your body by scratching once you’ve washed off the oil.

Poison ivy is diagnosed on the basis of symptoms — itching, redness, and bumps, blisters, or streaks on the skin. Questions that a healthcare professional may ask to help diagnose you include:

• Where you were
• What you were doing
• What you have may touched in the hours before symptoms appeared

You usually can treat poison ivy reactions yourself to alleviate discomfort.

The most important first step in treating any reaction is to ensure none of the plant’s oil remains on your skin, Dr. Zeichner says. Wash the affected area immediately with a gentle cleanser and thoroughly wash any exposed clothing, he says.

• Taking oral antihistamines, such as cetirizine (Zyrtec), loratadine (Claritin), or fexofenadine (Allegra)
• Using over-the-counter steroid creams, such as hydrocortisone, for the first few days
• Applying calamine lotion, which can reduce itching
• Soaking the affected area in a cool or lukewarm bath containing oatmeal or ½ cup baking soda
• Placing a cool, wet compress on the area for 15 to 30 minutes several times each day

When to See a Doctor for Poison Ivy

• A fever of more than 100 degrees F (37.8 degrees C)
• Pus or yellow scabs on your rash
• Increased swelling
• A rash that covers your eyes, mouth, or genital area
• A rash that covers large areas of your body
• Difficulty breathing
• No sign of improvement after a few weeks

Your doctor will conduct a visual assessment and review your history of symptoms and exposure to evaluate your condition.

If your reaction is severe enough to require medical treatment, your doctor may prescribe an oral steroid, such as prednisone, to reduce inflammation.

There’s a lot you can do to prevent a poison ivy reaction in the first place — both by reducing your risk of exposure and by acting quickly if you know you’ve been exposed.

Remove poison ivy from your property. In your own yard, you can get rid of poison ivy either by applying an herbicide or by pulling it out of the ground.

If you pull out the plant, wear heavy gloves and remove the roots along with the plant. Afterward, carefully remove the gloves and wash them and your hands thoroughly.

Wash clothing and objects after potential contact. Be sure to remove your clothing carefully — without letting it touch furniture, rugs, or appliances — and wash it promptly in a washing machine. Wash boots and shoes using detergent and water.

Serious complications from a poison ivy reaction are rare.

Swelling and breathing difficulties are the most troublesome problems to look out for, especially if your face swells or your eyes swell shut. This can result in lasting or serious damage.

Usually, the only lasting effects of a poison ivy reaction are cosmetic and fade away.

“Extremely severe cases theoretically can lead to scarring,” Zeichner says.

But more commonly, he says, a rash will leave behind a red or brown stain that will disappear in a few weeks.

Poison ivy isn’t the only plant that can cause a rash. Like poison ivy, poison oak and poison sumac contain the chemical urushiol and can cause the same allergic reaction and the same itchy skin and blisters.

• Not only is poison ivy common, but it also spurs the most common allergic reaction in the U.S.
• Symptoms, such as redness and a rash, usually resolve in three weeks or less.
• You can treat most poison ivy reactions at home.
• Prevention tactics include removing poison ivy from your property, wearing protective clothing when around the plant, and washing clothing that might be exposed to it.
• Call the doctor if your poison ivy reaction includes a high fever, difficulty breathing, or symptoms that get worse.