Poison Ivy: Prevention And Treatment

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Harvard Medical School
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Poison Ivy: Prevention And Treatment

Poison Ivy
Poison Ivy: Prevention And Treatment
Poison Ivy: Prevention And Treatment
The wicked itch and bothersome rash are the result of urushiol oil, a potent toxin.
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Reviewed by the Faculty of Harvard Medical School

Poison Ivy: Prevention And Treatment

It's the world's most common allergy, affecting nearly half of all Americans. Each year, about 50 million people get a reaction from poison ivy, sumac and oak — including many people who aren't allergic to anything else.

The wicked itch and bothersome rash are the result of urushiol oil, a potent toxin. Get as little as one-billionth of a gram on your skin and you might be scratching yourself silly. And a lot more than that billionth of a gram is released when the plant is disturbed through direct contact with its stem, leaves or roots. Here's how to prevent and treat poison plant reactions:


Dose yourself with deodorant
There are effective commercial products that can help keep the urushiol oil from getting into your skin. But in a pinch, try what members of the U.S. Forestry Service have done before venturing into nature: Spray some deodorant on your arms and legs. According to some dermatologists, the active ingredient in deodorants, aluminum chlorohydrate, can prevent urishiol from irritating the skin. Just be careful not to spray any on your face.

Don't be Touchy
You can spread urushiol-containing oils from one area of your body to others if you touch the contaminated area and get oils on your hands. It is also possible to acquire poison ivy, oak, or sumac by touching the fur of your pet, if the animal has contacted these plants.

Give yourself, clothing and tools a good wash — quickly
First the bad news: Since urushiol oil can remain potent for up to five years, you can get a reaction from touching tools or clothing that were used to dig up poison ivy years earlier. The good news: If you wash yourself and those items in soapy water within 10 minutes of contact, you can help to minimize the rash.

To remove the plant oil, it is best to first use a solvent that can separate the oil from your skin surface. Rubbing alcohol (isopropyl alcohol) is very effective. After wiping your skin with rubbing alcohol, you should rinse thoroughly with water. If you do not have a solvent available, it is still helpful to rinse thoroughly in water as quickly as possible after your contact with the plant.


The poison ivy rash develops one to two days after exposure. Once the rash develops, treatment focuses on relieving the symptoms, calming the inflamed skin and protecting it from infection, and helping blisters to heal.

Head to the kitchen for help
Calamine lotion can be very soothing for the itchy rash of poison ivy. Calamine lotion that is not diluted with water can form a thin crust over the rash, which can make it less sensitive. For mild cases this may be all you need. In treating children, avoid combination products that contain antihistamines because too much antihistamine can be absorbed through the skin. In both children and adults, a compress with ice-cold whole milk helps dry the rash and soothe the itch, but don't use skim milk: It's the fat in milk that helps.

Milk of magnesia also may help because it's an alkaline solution, like calamine. Because it's thinner than calamine, it can be easier to apply.

Apply ice
The fastest and cheapest treatment to temporarily soothe pain and itching is plain ice. If you have weeping or blisters, applying ice is not advised. For dry skin without blisters, it is safe to place a cube directly on the irritated skin for about one minute. The coolness of the ice helps soothe itching, if only temporarily.

From the Pharmacy
Without a prescription, you can buy oral antihistamines to control itching, such as chlorpheniramine (Chlor-Trimeton) and diphenhydramine (Benadryl). Many soothing topical lotions are available. Look for ones with low concentrations (0.5%) of camphor and/or menthol.

Get professional help
For severe cases, when the rash is all over the body, on the face, or blistering, you may need to visit your doctor for antihistamines, topical or oral steroids, all of which can effectively treat the rash and itching. Steroids are most helpful when they are initiated quickly after the rash appears.

Time Heals All
The rash from poison ivy, oak, or sumac clears without treatment after approximately two weeks. It is possible to have some residual itching, which can stay active longer if you scratch. If you have irritating itching once your blisters have healed, a prescription steroid cream from your doctor should bring relief.


Last updated December 03, 2009

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