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Leaves of three, let it be

Published in Family Medicine, Allergy & Asthma Author: Kristina Lelcu,MD

Whether you are camping, hiking or just taking a stroll by the lake, learn to recognize and avoid coming in contact with poison ivy. Remember the old warning, "Leaves of three, let it be." Look for three small leaflets. Each leaflet is oval-shaped and pointed at the tip. The middle leaflet has a longer stem than the side leaflets.

Poison ivy has an oil called urushiol. When this oil goes into the skin, most people will get an itchy rash from an allergic reaction. The first time you come in contact with the plant, the skin reaction may not appear until 12 to 21 days later. If you have had an allergic reaction to poison ivy in the past, the rash usually appears much sooner, within 12-72 hours after touching the plant.

Signs and symptoms

An allergic reaction to poison ivy will cause:

  • Very itchy skin
  • A rash: red, streaks or patches, swollen lines, blisters
  • Black marks may appear on the skin if the plant oil dries on the skin

The rash usually lasts seven days to three weeks.

What to do if you know you touched poison ivy

Most people can treat poison ivy at home. Do the following:

  • If you know your skin touched the oil, wash the skin with lukewarm water to inactivate and remove the oil. This is most effective if you can do it within 15 minutes of touching the oil.
  • If you shower, rinse your skin with lukewarm water before adding soap. Urushiol can stick to soap. If it sticks, the soap may spread the oil all over your body.
  • Be sure to clean under your fingernails.
  • Wash all the clothes you were wearing to remove the urushiol.
  • Wash everything else that was with you when you touched the plant (pets, leashes, tools, bicycles). Urushiol can stay on surfaces for a long time and cause an allergic reaction.

Treatment and relieving the itchy skin

While your skin is healing, try the following to relieve itching:

  • Take cool showers.
  • Put calamine lotion on the itchy skin.
  • Apply cool compresses to the itchy skin.
  • Hydrocortisone cream may help a mild case.
  • Take an oral antihistamine. Do not put an antihistamine on your skin, as it can make the itch and rash worse.
  • If the itching becomes too intense or the rash appears on most of your body, contact your health care provider. They may need to prescribe a prescription steroid ointment. In a severe case, you may need a strong medicine, such as prednisone.

Preventing exposure

  • Be able to identify poison ivy in nature. For more examples how it make look at various times of year, review the following photos from the Minnesota Department of Agriculture.
  • NEVER burn poison ivy. Doing so releases the plant’s oil into the air where it can cause serious respiratory problems.
  • If working in areas where poison ivy is present, consider applying a barrier cream beforehand — like Ivy Block (bentoguantam). This compound can prevent allergic reactions to poison ivy or lessen their severity.

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