Poisonous Plants: Poison Ivy, Poison Oak, and Poison Sumac

Three plants you really don’t want to touch for their rash-causing ability are poison ivy and two of its lesser-known cousins: poison oak and poison sumac. Here's a guide to help you deal with these troublesome plants, including little-known facts, and key tips to identify and remove them.

Six Fast Facts

Knowing these six often-misunderstood factoids about poison ivy, poison oak, and poison sumac can help you head off trouble:

1. All plant parts are poisonous

Some people think that it’s just the leaves of these plants that will cause skin rashes.

The truth is that the urushiol oil is in all plant parts, so it’s possible to get a rash from touching the flowers, fruits, stems, and even roots.

2. You don’t have to touch poison-ivy plants to get the rash.

Urushiol oil easily transfers from plants to objects to people – including tools, clothing, shoe bottoms, pets, even stray soccer balls retrieved from a weedy area.

It’s possible to get a rash without ever touching or even seeing a poison ivy/oak/sumac plant.

One preventive step is keeping the yard as weed-free as possible. Others include washing clothes immediately after working outside; bathing pets and washing objects that have gone into untended areas; wearing protective creams such as Ivy Block, Tecnu, Multi-Shield, or buji Block when working outside, and washing exposed skin ASAP with soap and water if you suspect you’ve contacted these plants or something that has.

Rashes usually can be stopped if you wash within 15 minutes of contact.

3. You can get a rash even in winter or when poison-ivy plants are dead.

Urushiol oil remains viable even in winter-dormant plants and soon after plants have died.

That means you can get a rash by pulling leafless vines in winter or handling plants after you’ve killed them with a weed-killer. Some people have had their worst rashes in winter.

Urushiol oil can remain rash-causingly viable for as long as five years after plants are dead.

4. You’re never guaranteed to be immune.

About 85 percent of the population gets rashes from poison ivy/oak/sumac.

Some people are more sensitive than others, with ages 5 to 20 being the most sensitive age range. Sensitivity tends to lessen from the 30s on.

However, just because you one day touch poison ivy/oak/sumac and don’t get a rash doesn’t mean you’re now safe. You could get a rash next touch – especially if you get more oil on your skin.

It’s also possible for people who never got a rash before to suddenly get one in older age.

You can’t build immunity by eating poison ivy/oak/sumac leaves either. That’s a dangerous myth that could cause a serious rash in your throat.

5. Burning or weed-whacking poison ivy/oak/sumac is even more harmful than touching it.

One of the worst ways to tackle these rash-causing plants is to cut them down with a string trimmer. That spews oil, throwing it on your clothes and possibly getting it in your eyes or nose.

Worst of all is burning yanked or dead poison ivy/oak/sumac plants. Urushiol oil gets in the smoke, and if that’s breathed, a very painful and possibly even fatal rash can affect your lung lining.

Never mow, weed-whack, or burn these plants – dead or alive.

6. The rash itself is not contagious.

You won’t get a rash by touching someone’s rash or blisters, which typically occur two to three days after oil exposure. However, there’s an outside chance you could get a rash if the person hasn’t washed oil from the skin.

The same goes for spreading the rash around your body. The fluid in the rash won’t spread the reaction, but any left-over oil could.

How to identify poison ivy, oak and sumac

Poison ivy

New leaves of poison ivy in spring. iNaturalist

Poison Ivy

Poison ivy is the most familiar of this plant family (Toxicodendron) that contains a severely skin-irritating oil called urushiol.

  • Can be found throughout almost all of the continental U.S.
  • Leaves grow in clusters of three with the middle leaf being slightly bigger than the two on either side.
  • The leaves start out reddish in spring, then become a shiny green in summer before turning various shades of red, orange, and yellow in fall.
  • Plants produce small, waxy white berries in late summer that turn red in fall.
  • As the vines age, the stems become woody and put out distinctive “hairy” root growths.

Poison Oak

  • Grows as a low shrub in the eastern and southern U.S.
  • Can develop into taller, more vine-like plants on the West Coast.
  • Produces clusters of three leaves that are more fuzzy and green.
  • Poison oak flowers are yellow to green
  • Berry clusters are green-yellow or white.
Pacific poison oak

Pacific poison oak. iNaturalist

Atlantic poison oak

Atlantic poison oak. iNaturalist

Poison Sumac

Poison Sumac. iNaturalist

Poison Sumac

  • Poison sumac is much less common, although just as potent in the rash department.
  • Found mainly in eastern U.S. wetlands
  • Grows as a woody shrub or small tree growing up to 20 ft. tall.
  • Leaves are smooth and velvety
  • Flowers and fruits are similar to its two cousins, except the clusters tend to hang more loosely.

How to get rid of poison ivy, oak and sumac plants

Existing plants will have to be cut down, pulled out, or sprayed with herbicides. Be sure to cover all skin before touching potentially rash-causing weeds. Be sure to wear gloves, protective clothing, and eyewear while handling plants. Barrier skin creams that create a protective barrier to shield the skin from plant-oil contact may help prevent a reaction. Examples include Ivy Block, Multi-Shield and Buji Block.

If possible remove plants with their roots when they are young and more shallowly rooted. For more established plants, repeated cutting and digging of established plants will sap energy and eventually kill them. Cut the vine or shrub close to the ground and immediately apply an herbicide to the fresh cut with a brush. Any regrowth can be treated with an herbicide, applying to individual leaflets.

Place cut portions of plants in a plastic bag and dispose of it. Take precautions when removing dead, or leafless poison plants in winter. All parts of the plant contain urushiol, and the oil continues to cause rashes for years after a plant has died.

How to avoid a rash after contact

After brushing against or handling plants, wash the urushiol off your skin, clothing, and any tools or equipment that’s been in contact with the plant.

Wash skin with soap and cool running water as soon as possible afterward. Never wash skin that has come into contact with poison ivy, oak or sumac with hot water. Hot water opens the pores in your skin making it easier for the urushiol to penetrate deeper into your skin.

Wash all gloves and garments in very hot water separately from a general laundry load to remove the rash-causing oil from the fabric. Clean contaminated tools thoroughly with rubbing alcohol or soap and water.

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