What Is Poison Ivy? Symptoms, Causes, Diagnosis, Treatment, and Prevention
Poison ivy is a toxic plant that’s common in most of the continental United States. When it touches your skin, it can cause a rash known as contact dermatitis. This rash may develop into increased redness, swelling, and blisters, which are often itchy or painful.
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.
Symptoms of a skin rash may include:
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.
Getting more of the oil on your skin may also cause a rash to develop sooner.
If you inhale smoke containing the oil from poison ivy, symptoms may include irritation in your airway and lungs, a facial rash, and difficulty breathing.
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 the oil comes into contact with an object and isn’t washed off afterward, it’s possible to have a skin reaction after touching that object — even years later.
“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.
When the oil from poison ivy touches your skin, it bonds to the area and causes a reaction from your body’s own immune system. This reaction is known as allergic contact dermatitis.
About 85 percent of people in the U.S. may have an allergic reaction to poison ivy, with 10 to 15 percent susceptible to a severe reaction.
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.
If a skin rash appears to spread, it’s probably because the area was already exposed and it’s experiencing a delayed reaction. You also may have oil from the plant under your fingernails or have unknowingly touched a contaminated item.
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
Typically, however, a doctor can diagnose a poison ivy reaction by looking at your rash. Other tests usually are not necessary.
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.
After you’ve removed any remaining plant oil, you can help soothe your rash with the following remedies:
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
If your reaction is serious or widespread, you’ll need to seek treatment to help alleviate your discomfort and limit the risk of serious complications. A doctor can prescribe corticosteroids, which is usually the first line of treatment.
Situations in which a poison ivy reaction requires medical attention include:
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.
Your doctor also may prescribe an oral antibiotic if you’ve developed a bacterial infection in the area.
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.
Avoid areas where poison ivy thrives. If you’re hiking or camping, stay on designated trails or campsites and away from areas where you know poison ivy plants have returned after being cleared.
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.
Never burn poison ivy that you’ve removed. The smoke will contain the plant’s toxic oil. Seal the plant in a heavy-duty garbage bag and place it in the trash.
Wear protective clothing. Sometimes it’s not possible to avoid areas prone to poison ivy growth — especially if you work outdoors. Depending on your activity, it can help to wear long pants tucked into boots, as well as long sleeves tucked into protective gloves.
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.
It’s also a good idea to wash items such as gardening tools and recreational gear. Remember to wear long dishwashing gloves while washing or handling any potentially exposed item.
Wash your skin after known or potential contact. Even if your skin touches poison ivy, you can still prevent or limit an allergic reaction by cleaning it with soap and water within a half hour of contact. Even after an hour, you can limit the severity or any reaction by washing.
Teach your family and friends to recognize the plant. Once you know about poison ivy, educate your family and friends so you can all look out for one another when you are outdoors.
Mind your pets. Although it is rare for pets to get a reaction from poison ivy, they can spread its oil to humans.
Try not to let your pet wander into areas where poison ivy may grow. If you think your pet may have been exposed, give the animal a bath using an appropriate shampoo while wearing rubber or vinyl gloves.
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.
Your poison ivy rash also can get infected, especially if you scratch the area and break open blisters. Bacteria under your fingernails are often the source of this infection, which may need to be treated with antibiotics.
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.
As many as 50 million Americans have a poison ivy reaction each year, making it the most common allergic reaction in the U.S.
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.
Several other common plants can irritate your skin, although some of them cause only temporary stinging or burning. Others, such as giant hogweed, can provoke a more serious, longer-lasting reaction.
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.
