Overview

Poison ivy rash Open pop-up dialog box Close Poison ivy rash Poison ivy rash Brushing against a poison ivy plant can cause a red, itchy rash with swelling, bumps and blisters. Frequently, the rash takes a linear form (as in the top-left corner of the photo) due to the way the plant sweeps across the skin.

Poison ivy rash is caused by an allergic reaction to an oily resin called urushiol (u-ROO-she-ol). This oil is in the leaves, stems and roots of poison ivy, poison oak and poison sumac.

Wash your skin right away if you come into contact with this oil, unless you know you're not sensitive to it. Washing off the oil may reduce your chances of getting a poison ivy rash. If you develop a rash, it can be very itchy and last for weeks.

You can treat mild cases of poison ivy rash at home with soothing lotions and cool baths. You may need prescription medication for a rash that's severe or widespread — especially if it's on your face or genitals.

Products & Services Book: Mayo Clinic Book of Home Remedies

Symptoms

Signs and symptoms of a poison ivy rash include:

Redness

Itching

Swelling

Blisters

Difficulty breathing, if you've inhaled the smoke from burning poison ivy

Often the rash looks like a straight line because of the way the plant brushes against your skin. But if you come into contact with a piece of clothing or pet fur that has urushiol on it, the rash may be more spread out. You can also transfer the oil to other parts of your body with your fingers. The reaction usually develops 12 to 48 hours after exposure and lasts two to three weeks.

The severity of the rash depends on the amount of urushiol that gets on your skin. A section of skin with more urushiol on it may develop a rash sooner.

Your skin must come in direct contact with the plant's oil to be affected. Blister fluid doesn't spread the rash.

When to see a doctor

See your doctor if:

The reaction is severe or widespread

You inhaled the smoke from burning poison ivy and are having difficulty breathing

Your skin continues to swell

The rash affects your eyes, mouth or genitals

Blisters are oozing pus

You develop a fever greater than 100 F (37.8 C)

The rash doesn't get better within a few weeks

Causes

Poison ivy plant Open pop-up dialog box Close Poison ivy plant Poison ivy plant A poison ivy plant typically has three leaflets branching off a single stem. It may grow as a low plant or bush or as a vine. Low-lying poison ivy plants are usually found among groups of weeds and other plants.

Poison ivy plant with berries Open pop-up dialog box Close Poison ivy plant with berries Poison ivy plant with berries Poison ivy leaves vary greatly in their shape, color and texture. Some leaves have smooth edges, while others have a jagged, tooth-like appearance. In the fall, the leaves may turn yellow, orange or red. Poison ivy can produce small, greenish flowers and green or off-white berries.

Poison ivy plant Open pop-up dialog box Close Poison ivy plant Poison ivy plant Poison ivy grows three leaves per stem. It grows as vines or low shrubs in most climates.

Poison sumac plant Open pop-up dialog box Close Poison sumac plant Poison sumac plant The poison sumac plant has smooth-edged leaves and can grow as a bush or tree. Unlike poison ivy and poison oak, it doesn't grow in a three-leaf-per-stem pattern.

Poison ivy rash is a type of allergic contact dermatitis caused by an oily resin called urushiol. It's found in the leaves, stems and roots of poison ivy, poison oak and poison sumac. This resin is very sticky, so it easily attaches to your skin, clothing, tools, equipment and pet's fur. You can get a poison ivy reaction from:

Direct touch. If you touch the leaves, stem, roots or berries of the plant, you may have a reaction.

If you touch the leaves, stem, roots or berries of the plant, you may have a reaction. Touching contaminated objects. If you walk through some poison ivy and then later touch your shoes, you may get some urushiol on your hands, which you may then transfer to your face or body by touching or rubbing. If the contaminated object isn't cleaned, the urushiol on it can still cause a skin reaction years later.

If you walk through some poison ivy and then later touch your shoes, you may get some urushiol on your hands, which you may then transfer to your face or body by touching or rubbing. If the contaminated object isn't cleaned, the urushiol on it can still cause a skin reaction years later. Inhaling smoke from the burning plants. Even the smoke from burning poison ivy, poison oak and poison sumac contains urushiol and can irritate or harm your nasal passages or lungs.

A poison ivy rash itself isn't contagious — blister fluid doesn't contain urushiol and won't spread the rash. And you can't get poison ivy from another person unless you've touched urushiol that's still on that person or his or her clothing.

Risk factors

Outdoor activities such as the following can put you at higher risk for exposure to poison ivy, poison oak and poison sumac:

Farming

Forestry

Landscaping

Gardening

Firefighting

Construction

Camping

Fishing from the shoreline or hunting

Cable or telephone line installation

Complications

If you scratch a poison ivy rash, bacteria under your fingernails may cause the skin to become infected. See your doctor if pus starts oozing from the blisters. Treatment generally includes antibiotics.

Prevention

To prevent poison ivy rash, follow these tips: