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Allergies to Poison Ivy, Oak, and Sumac

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How Common Are Poison Plant Allergies?

Poison ivy, poison oak, and poison sumac are three of the most common causes of allergic contact dermatitis in North America. Some experts estimate that three out of four people are sensitive to the chemical found in these plants, although the degree of sensitivity varies. Some people are very sensitive and will have a quick reaction upon contact with a small amount of urushiol. For those who are less sensitive, exposure to a large amount of urushiol is necessary before a reaction develops. Cases of poison plant allergy occur most frequently during the spring, summer, and early fall when people spend more time outdoors.

How Are Allergies to Poison Plants Diagnosed?

An allergy to a poison plant is diagnosed based on the typical pattern of symptoms and the appearance of the rash.

How Are Allergic Reactions to Poison Plants Treated?

An allergic reaction to a poison plant cannot be cured, but the symptoms can be treated. You may take cool showers and apply an over-the-counter lotion -- such as calamine lotion -- to help relieve the itch. If your reaction is more severe or involves mucus membranes (membranes found in the eyes, nose, mouth, and genitals), you may need a prescription drug, such as prednisone, to help control the reaction.

How Long Does a Poison Plant Rash Last?

Most rashes caused by poison ivy, poison oak, or poison sumac are mild and last from five to 12 days. In severe cases, the rash can last for 30 days or longer.

Does Immunotherapy Help With Poison Plant Allergies?

Immunotherapy is not available for allergies to poison ivy, poison oak, and poison sumac.

How Can Poison Plant Reactions Be Prevented?

You can take steps to prevent poison plant reactions with the following tips:

  • Learn to identify poison ivy, poison oak, and poison sumac, and avoid contact with them.
  • Remove these plants from around your home, especially in areas where you may be working or playing.
  • When walking in the woods or working in areas where these plants may grow, cover your skin as much as possible by wearing long pants, long-sleeves, shoes, and socks.
  • Do not let pets run in wooded areas where they may be exposed to the poison plants. They can carry urushiol back home on their fur.

Is a Poison Plant Rash Contagious?

Many people think a poison plant rash can be spread from one part of the body to another or from person to person. In general, this is not true. You can spread the rash only if you have urushiol on your hands. Also, it can take longer for the rash to appear on certain areas of the body, especially areas such as the soles of the feet where the skin is thicker. This may give the appearance that the rash has spread from one part of the body to another. You can also be re-exposed to the urushiol by touching gardening tools, sports equipment, or other items that were not cleaned after being in contact with the plants. Scratching or touching the rash and fluid from blisters will not cause the rash to spread because urushiol is not present in the blister fluid.

WebMD Medical Reference

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