Poison Ivy, Poison Oak and Poison Sumac

What is poison ivy?

Poison ivy is a common poisonous plant that causes an itchy skin rash. Other rash-inducing poisonous plants include poison oak and poison sumac. These plants produce an oily sap called urushiol that brings on an irritating, itchy allergic reaction. When you touch a poisonous plant or an object that’s been in contact with a plant, you develop an itchy rash. This rash is a form of allergic contact dermatitis.

How common is a poison ivy rash?

Up to 90% of people who come into contact with poison ivy oil develop an itchy rash. You don’t have to be exposed to much: 50 micrograms of urushiol — an amount smaller than a grain of salt — is enough to cause a reaction.

Who might get a poison ivy rash?

Nearly everyone who touches urushiol gets a poison ivy rash. You’re more likely to come into contact with a poisonous plant if you have one of these jobs or hobbies:

• Camper or hiker.
• Farmer or gardener.
• Groundskeeper or landscaper.
• Forestry worker.
• Forest firefighter.
• House painter.
• Roofer.

What do poisonous plants look like?

Poisonous plants grow all over the continental United States. Each type has a distinctive appearance:

• Poison ivy: Poison ivy is most known for its leaves. Each leaf has three leaflets. A popular saying is, “Leaves of three, let them be.” Poison ivy grows as a shrub and a vine. Its summer-green leaves turn reddish in the spring and yellow, orange or red in the fall. A poison ivy shrub may have white berries.
• Poison oak: The leaves have three leaflets like poison ivy, but with rounded tips. The leaves’ undersides are fuzzy and lighter in color than the top. Poison oak grows as a shrub. It’s most common in the western United States. The shrub sometimes has white or yellow berries.
• Poison sumac: This tall shrub or small tree has drooping clusters of green berries. (Nonpoisonous sumacs have red, upright berries. Contact with nonpoisonous sumacs won’t cause an allergic rash.) Each leaf has clusters of seven to 13 smooth leaflets arranged in pairs. Poison sumac thrives in wet, swampy regions.

What causes a poison ivy rash?

Poison ivy, poison oak and poison sumac produce an oil called urushiol. Almost everyone is allergic to this oil. When your skin touches the oil, an allergic reaction occurs. The itchy rash that develops is a type of allergic contact dermatitis.

What are the symptoms of a poison ivy rash?

Urushiol oil causes the same allergic reaction — an itchy skin rash — no matter what poisonous plant you touch. Depending on your skin’s sensitivity, a rash may develop within a few hours or days after initial contact. Symptoms include:

• Blisters.
• Itchy skin rash.
• Redness and swelling.

How is a poison ivy rash diagnosed?

Your healthcare provider will look at the rash, assess your symptoms and ask questions to determine if you could have encountered a poisonous plant. Other allergens and irritants besides poisonous plants can cause contact dermatitis or an itchy rash. If you haven’t been outdoors or in contact with plants, your healthcare provider will want to rule out other skin conditions or causes.

How is a poison ivy rash managed or treated?

Rashes from poisonous plants usually go away within a week or two. In the meantime, these over-the-counter medications can relieve the itchy rash:

• Anti-itch creams, including calamine lotion (Caladryl®) and hydrocortisone creams (Cortizone®).
• Antihistamines, such as diphenhydramine (Benadryl®).
• Colloidal oatmeal baths (Aveeno®) and cold compresses to soothe itching.

Your healthcare provider may prescribe an oral steroid, such as prednisone, if the rash becomes more severe or the rash forms on the mucous membranes of the eyes, nose, mouth or genitals.

What are the complications of poison ivy exposure?

Some situations increase your risk of problems if you’re exposed to poison ivy, poison oak or poison sumac. These factors include:

• Inhaling smoke: When poisonous plants burn, they release urushiol into the air. You may develop a rash inside of your nasal passages, mouth and throat from inhaling the smoke. Oil in the air also affects the lungs and can cause serious breathing problems.
• Scratching: It’s hard not to scratch this itchy rash. But you can get an infection if you scratch until skin bleeds. Bacteria from under your fingernails can get inside any open wound.

Can a poison ivy rash spread to other parts of the body?

No. It might look like a rash is spreading, but you’re actually developing new rashes on areas of skin that came into contact with urushiol oil. You might have touched a plant in some areas and not even realized it — for example, if a backpack strap brushed against plants and then touched your bare shoulder. Some rashes take longer to develop. The extent of the rash depends on your skin sensitivity and how much oil you touched.

Is a poison ivy rash contagious?

You can’t get a poison ivy rash by touching another person’s rash. But you could develop a rash if you touch the oil on another person’s body or clothes. You can also come in contact with the oil by touching your pet’s fur or a contaminated item like a gardening tool or camping gear.

How can I prevent a poison ivy rash?

The best way to avoid developing this itchy rash is by learning what poisonous plants look like so you can avoid them.

If you think you’ve come in contact with a poisonous plant, you can:

• Apply isopropyl (rubbing) alcohol to exposed body parts, gardening tools or other contaminated items to strip away the oil.
• Scrub under your fingernails with a brush.
• Use dishwashing soap and cool water to wash hands that have touched a poisonous plant.
• Wash clothes after being outdoors.
• Wear long sleeves, pants and gloves when doing yard work, gardening, farming or hiking.
• Wear rubber gloves while bathing pets that have been in contact with poisonous plants.

What is the prognosis (outlook) for people with a poison ivy rash?

Most poison plant rashes cause mild (but annoying) symptoms that go away within a week or two. Rarely, a skin rash lasts for longer than a month. Try not to scratch. Scratching can break open skin and cause an infection.

When should I call the doctor?

Reach out to your healthcare provider if you have a poison plant rash and you experience:

• Rash covering more than a quarter of your body.
• Rash on the mucous membranes of the eyes, nose, mouth or genitals.
• Red streaks, fever or other signs of infection.
• Signs of anaphylaxis, including breathing difficulties, hives and swelling.

What questions should I ask my doctor?

If you have a poison plant rash, you may want to ask your healthcare provider:

• Do I need any testing to confirm the rash is from a poisonous plant?
• How can I avoid getting this rash again?
• How can I keep my family members from getting this rash?
• What treatments can I use to reduce itching?
• How long will the rash last?
• Should I look out for signs of complications?

A note from Cleveland Clinic

It’s hard not to scratch an itchy poison ivy rash. Fortunately, most rashes clear up with minimal treatment within a week. Ask your healthcare provider for suggestions to stop the itch. And remember, don’t scratch! You might temporarily feel better, but scratching can introduce bacteria into the skin and cause an infection.