Plan & Prepare

Poison Ivy, Poison Oak, and Rashes

Exposure to certain plants like poison ivy and poison oak can cause skin irritation, incessant itching, and a spreading rash. Other toxic plants such as poison sumac can cause irritation as well.

You can often recognize poison oak and poison ivy by the saying, “leaves of three, let it be.” However, the color and size of the plants can change through the year, making recognition a challenge. Knowing the appearance of toxic plants is an important part of traveling safely outdoors.

People have different sensitivities to the sap of these plants, and the resin (called urushiol) binds to the skin within thirty to sixty minutes. Even very slight contact (like brushing against the leaves) is enough to leave the oil behind. The resin can be spread on clothing, camping equipment, or pet fur. It can last for years if it’s not washed off with soap and water or commercially available solutions.

You can develop a rash by touching the plant or touching the oil on someone else’s skin, but the rash (and blister fluid) itself is not contagious. You cannot spread the rash from person to person. The rash can occur within several hours to as long as three weeks post-exposure. The spread of blisters is due to the resulting allergic reaction in the body.

Symptoms and Description

Poison oak and ivy both have three leaves, one in the center and one on each side of a central stem. Poison ivy has smooth or slightly notched almond-shaped leaves, and the plant can be a low-lying scrub or a bushy climbing vine or hedge. (image.poisonivy.jpg)

Poison oak is similar but with larger, more rounded scalloped-edged leaves. It grows as a scrub or hedge.

Both poison oak and ivy can grow white or yellow berries in the fall. Their leaves can be light red and green in the spring; shiny or dark green in the summer; and bright orange, yellow, or red in the autumn.

Poison sumac has seven to thirteen leaflets per stem. One leaf is situated at the end with the rest arranged in opposite pairs. These leaves are smooth with pointed tips. Poison sumac is a woody shrub or tree and may have glossy pale yellow or cream-colored berries. (image.poisonsumac.jpg)

The body’s allergic response to poison sumac differs from person to person. Reactions may be delayed for days to weeks after the initial exposure and can then last for several weeks. Long after the oil has been washed off the skin, the rash can still spread to different areas of the body due to one’s allergic response. The rash can be extremely itchy and uncomfortable and can lead to very severe blistering. The rash from urushiol exposure has patches of red with streaks or clusters of clear blisters. The blisters can become large and ooze clear or yellowish fluid. The blisters will eventually crust and flake off over several weeks.


  • Areas of intensely itchy skin.
  • Streaks or patches of red slightly raised skin.
  • Clusters of blisters that can break open and ooze clear or yellowish fluid.

Guidelines for Safe Travel

Awareness of geographic areas infested with poison oak, ivy, and sumac is the first step toward safe outdoor travel.

Consider wearing taller socks or long pants and carry soap or a commercially available scrub to rinse off potential urushiol oil after exposure. Remember your canine friends too. If your dog has been running through toxic plants, the oils can easily spread to human skin.

Avoid burning toxic plants, as smoke exposure can cause an allergic reaction to the eyes, mouth, and throat and even cause breathing problems.


  • Familiarize yourself with the appearance of poison oak, ivy, and sumac in your area before heading out.
  • Educate your children to avoid touching the plants.
  • Consider long socks, pants, and sleeves to avoid contact with toxic plants that can line trails.
  • If you have come into contact with suspicious plants, wash the exposed area well with soap and water or commercially available solutions.
  • Wash all your clothes, shoes, and equipment as soon as possible post-exposure with soapy water. Residual oils can cause later infections.
  • Do not burn toxic plants.
  • Rash Treatment
  • If a rash develops, you can apply calamine lotion to the itchy areas.
  • Itching can be relieved with hydrocortisone cream, oral diphenhydramine, and/or oatmeal baths.
  • If a severe rash develops, you may need a two-week course of prescription steroids.
  • Avoid itching the rash, as skin breakdown can lead to a bacterial infection.
  • Watch for the development of spreading redness and swelling at the site of the rash, which may be a bacterial infection of the skin.

Emergency Red Flags

A rash from a toxic plant may necessitate evacuation if the itchiness is too uncomfortable to continue the trip. The level of discomfort, the severity of the rash, or involvement of certain body parts may require medical intervention. Always be aware that any break in the skin can lead to a bacterial infection.

  • Any rash that involves the eyes, genitals, mouth or throat, or breathing.
  • Skin irritation that is too uncomfortable to continue the trip.
  • Any signs of infection to skin (e.g., spreading redness, warmth, and/or pus).

Are you concerned about a rash?

Download GOES to launch a digital medical assessment or speak with a wilderness medicine physician.