“Leaves of three, let them be” is a phrase often used to identify plants that cause poison ivy dermatitis (rash). Generally, poison ivy and poison oak have three leaflets per leaf with flowering branches on a single stem. Poison sumac has five, seven, or more leaflets per leaf that angle upward toward the top of the stem.

When the skin comes in direct contact with these plants, a rash can develop.  This is because poison ivy, poison oak, and poison sumac plants contain an irritating oil that is found in the fruit, leaves, stem, roots, and sap of the plant. There are several ways that you can be exposed to the oil:

  • By touching the sap or rubbing against the leaves of the toxic plant at any time of year
  • By touching something that has the oil on it, such as animal fur or garden tools
  • By breathing in smoke when toxic plants are burned

After contact with the plant oil, about 50 percent of people develop signs and symptoms of poison ivy rash. The symptoms and severity differ from person to person. The most common signs and symptoms of poison ivy rash are:

  • Intense itching
  • Skin swelling
  • Skin redness

These symptoms usually develop within four hours to four days after exposure to the oil. After the initial symptoms, allergic individuals develop fluid-filled blisters in a line or streak-like pattern. Although the rash usually goes away within 1-3 weeks on its own, certain treatments can be used to relieve symptoms of itching, soreness and discomfort. To relieve the symptoms, you can:

  • Avoid scratching (that makes the itch worse)
  • Take an oatmeal bath
  • Try putting a cold, wet cloth or paper towels on your rash
  • Use calamine lotion
  • Use skin products that have aluminum acetate in them, such as Domeboro Solution, if your blisters have started to pop

If you have a very bad rash, your doctor or nurse can prescribe medicines called steroids. These medicines can reduce swelling and relieve itching. Steroids come in creams, ointments, and pills. Your doctor or nurse will decide what form you should use.

Steroid creams and ointments, such as hydrocortisone 1% cream, are also sold without a prescription, and may be used for mild cases.

Some creams or lotions can make your rash worse — The products listed below sometimes cause a reaction that makes your skin more itchy or irritated:

To prevent poison ivy rash, you should:

  • Stay away from poison ivy, even if the plant is dead
  • Wear long sleeves and pants when working near poison ivy, and wash your clothes right away when you are done. Keep in mind that the resin and oils from the toxic plants can be carried on clothing, pets, and under fingernails.
  • Wear thick vinyl gloves when doing yard work (latex and rubber gloves do not always protect against poison ivy)
  • Gently wash with soap (Dawn) and hot water if you do touch poison ivy (do not scrub), and remove any contaminated clothing. Washing within 10 minutes after exposure can reduce the likelihood and severity of symptoms.
  • Avoid burning poison ivy plants, which can irritate the skin and lungs.
  • Creams and ointments that create a barrier between the skin and the oil may be effective for people who are frequently exposed to poison ivy. Ivy Block is one type of barrier cream that may prevent poison ivy rash. It must be reapplied every four hours and it leaves a clay residue on the skin.1


  1. Patient education: Poision ivy (Beyond the basics). UpToDate. 2017. Available at: https://www-uptodate-com.ezproxy2.umc.edu/contents/poison-ivy-beyond-the-basics?source=related_link. Accessed June 26, 2017.