Poison ivy

Allergy to poison ivy, poison oak and poison sumac is estimated to occur in close to 70 percent of all individuals.  The chemical that is responsible for the skin reaction is found in the sap of these plants and is called urushiol.  

Exposure can occur with direct contact with the plant leaves or indirectly from touching something that has the chemical on it (pets, garden tools and clothing).  Airborne exposure can also occur through burning plants.  The chemical attaches to the skin and causes the body’s immune system to attack the skin containing the urushiol.  This leads to inflammation.

The symptoms of the allergic reaction are well-known: redness, swelling, warmth, blistering and, of course, itching.  Many times it’s easy to identify a poison ivy rash because of the characteristic linear pattern where the leaves of the plant brushed across an exposed area of the skin, such as an arm or a leg.  Other times it’s more difficult to distinguish the allergic reaction from other rashes such as bug bites, especially in the earlier stages of inflammation.  

So what do you do if you’re exposed?  First, cleanse the area with plain soap and water to remove any urushiol.  Between five minutes to five hours after exposure, the chemical will bind to the skin unless it is removed.  After it binds, soap and water is ineffective in removing it.  Thicker skin areas, such as the palms, will hold the chemical longer before it binds, so it could be transferred to other areas of the body.  Cleanse the hands thoroughly.   

Next, remove and wash any clothing that may have come in contact with the chemical.  Remember, the rash is not contagious.  It’s the chemical that is causing the troubles.
What if you develop symptoms?  Itching from mild reactions can be treated with over-the-counter (OTC) topical remedies such as calamine, oatmeal baths and lotions.  Avoid using topical lotions or creams that contain antihistamines (diphenhydramine) or anesthetics (benzocaine) as these can sometimes worsen a rash by sensitizing your skin. Hydrocortisone creams and oral antihistamines can treat both the allergic reaction and the itch.  Cool compresses may provide temporary relief of itching.  

Scratching the rash will not spread the chemical once it is bound to the skin.  The fluid in blisters does not contain the chemical.  However, scratching can break the skin, allowing normal skin bacteria to cause an infection.

More severe eruptions or rashes on the face or around the eyes may need prescription treatments such as oral steroids.  These are the most potent medicines available for treatment, but they must be used with caution due to their possible side effects.  It is usually best to see your physician if symptoms worsen, are rapidly progressive or are not controlled with conservative measures.

Remember, protect yourself outdoors if you are allergic to these plants.  Avoid going into poison ivy infested areas and wear long sleeves and pants if it’s unavoidable.

The content in this column is for informational purposes only.  Consult your physician for appropriate individual treatment.  Dr. Reynolds practices family medicine in Chesterfield.

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