How Poison Ivy Works

Poison Ivy Symptoms and Treatment
A crusty poison ivy leg rash
A crusty poison ivy leg rash
Photo courtesy Theresa L. Ford

­In ­the places where your skin has come into contact with poison ivy leaves or urushiol, within one to two days you'll develop a rash, which will usually itch, redden, burn, swell, and form blisters. The rash should go away within a week, but it can last longer. The severity of the reaction often has to do with how much urushiol you've touched. The rash may appear sooner in some parts of the body than in others, but it doesn't spread -- the urushiol simply absorbs into the skin at different rates in different parts of the body. Thicker skin such as the skin on the on soles of your feet, is harder to penetrate than thinner skin on your arms and legs.

Call your doctor if you experience these more serious reactions:

  • Pus around the rash (which could indicate an infection)
  • A rash around your mouth, eyes, or genital area
  • A fever above 100 degrees
  • A rash that does not heal after a week

Any of the following symptoms require immediate emergency medical assistance:

  • Swelling of the throat, tongue, or lips and/or difficulty swallowing
  • Difficulty breathing
  • Weakness
  • Dizziness
  • Bluish lips

The quicker you treat poison ivy, the greater the odds that you can remove at least some of the urushiol before it gets into your skin, and you may be able to ward off a reaction. As soon as you notice that you've touched poison ivy (or poison oak or sumac):

Over-the-counter corticosteroid creams can relieve itching.
Photo courtesy HowStuffWorks Shopper
  1. Rinse off your skin immediately with water. Rinsing within the first five minutes of contact is most effective.
  2. Remove all clothes that have come in contact with the plant and wash them with soap and water.
  3. Wash your skin with soap and cool water.
  4. Using a cotton ball, cleanse the affected areas of your skin with isopropyl (rubbing) alcohol.

Once the rash appears, you'll most likely be very itchy, but try not to scratch. Although breaking the blisters by scratching can't spread the rash, the bacteria under your skin can cause an infection and leave scars.

The rash should go away on its own within two weeks. If you're in a lot of discomfort, you can use wet compresses or soak the affected areas in water. You can also apply a topical corticosteroid (over-the-counter brands such as Cortaid and Lanacort), or take an over-the-counter antihistamine (such as Benadryl) to relieve the itching. Prescription cortisone can stop the reaction, but only if it is taken soon after exposure. Other topical products that can soothe itching are calamine lotion, zinc oxide ointment, baking soda paste (3 teaspoons baking soda and 1 teaspoon water), or an oatmeal bath (Aveeno).

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