Overview

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.

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 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.
  • 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.
  • 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:

  • Avoid the plants. Learn how to identify poison ivy, poison oak and poison sumac in all seasons. When hiking or engaging in other activities that might expose you to these plants, try to stay on cleared pathways. If camping, make sure you pitch your tent in an area free of these plants.

    Keep pets from running through wooded areas so that urushiol doesn't accidentally stick to their fur, which you then may touch.

  • Wear protective clothing. If needed, protect your skin by wearing socks, boots, pants, long sleeves and vinyl gloves.
  • Remove or kill the plants. In your yard, you can get rid of poison ivy by applying an herbicide or pulling it out of the ground, including the roots, while wearing heavy gloves. Afterward remove the gloves and thoroughly wash them and your hands. Don't burn poison ivy or related plants because the urushiol can be carried by the smoke.
  • Wash your skin or your pet's fur. Within 30 minutes after exposure, use soap and water to gently wash off the harmful resin from your skin. Scrub under your fingernails too. This helps prevent a rash. Even washing after an hour or so can help reduce the severity of the rash.

    If you think your pet may be contaminated with urushiol, put on some long rubber gloves and give your pet a bath.

  • Clean contaminated objects. If you think you've come into contact with poison ivy, wash your clothing promptly with detergent — ideally in a washing machine. Handle contaminated clothes carefully so that you don't transfer the urushiol to yourself, furniture, rugs or appliances.

    Also wash any other contaminated items — such as outdoor gear, garden tools, jewelry, shoes and even shoelaces — as soon as possible. Urushiol can remain potent for years. So if you put away a contaminated jacket without washing it and take it out a year later, the oil on the jacket may still cause a rash.

  • Apply a barrier cream. Try over-the-counter skin products that are intended to act as a barrier between your skin and the oily resin that causes poison ivy rash.
Aug. 11, 2015
References
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