Poison Ivy Plant Profile

Toxicity and Special Considerations

Close-up of Poison Ivy toxic plant (Toxicodendron radicans)
Douglas Sacha / Getty Images

Poison ivy is a weed commonly found growing in yards, along roadsides, in forests, and even in urban areas in North America. Its toxicity is based on an active irritant principle known as "urushiol," an oily resin contained in all parts of the plant. When urushiol comes into contact with any part of the skin or internal organs of a person, it can cause a rash. Pets are less likely to be troubled by poison ivy but are occasionally affected by it as well.

1:27

8 Facts About Poison Ivy You Need to Know

Toxicity of Poison Ivy

Poison ivy rash is classified as a type of contact dermatitis. Urushiol causes a reaction, and that reaction is manifested in a rash. But this reaction is specifically an allergic reaction, which is why some people are more likely to come down with poison ivy than others: If you're not allergic to urushiol, then you're not going to get poison ivy.

Some people experience poison ivy's toxicity as a very serious rash that requires treatment from a doctor, while others experience it merely as an irritating rash that can be soothed by over-the-counter balms or home remedies such as jewelweed (Impatiens capensis), which is found growing in backyards in North America almost as often as poison ivy is.

All parts of the poison ivy plant are poisonous, not just the leaves. The plant is also toxic at all times of the year, even in winter. This is one reason why it's important to be able to identify it by more than just the appearance of its leaves: Otherwise, you may not know that the now leafless plant in front of you is poison ivy, and, upon accidentally touching it, you could develop a rash. Even contact with urushiol on dead poison ivy plants (or urushiol that has rubbed off onto walls, fences, etc.) can cause the rash because it stays viable for five years.

Moreover, it is not only touching this noxious weed that is problematic. There are two other ways for humans to get poison ivy. Never eat poison ivy or allow young children to accidentally eat any: Ingesting it can cause a rash to develop in your digestive tract. In animals, eating poison ivy generally has less severe consequences.

Warning

Never burn poison ivy. Inhaling the smoke can cause a rash to develop on the lining of your lungs.

While dogs and cats can also get poison ivy, they're less likely to because they are usually protected from direct skin contact by their fur coats. But dogs and cats that eat poison ivy can experience gastrointestinal upset. A related issue is that, while the poison ivy rash, itself, is not contagious, any object smeared with urushiol becomes contaminated. This means that, if your dog brushes up against poison ivy, then you pet your dog, the urushiol is transferred onto your hand, and you can come down with the rash.

Symptoms of Poison Ivy Reactions in Humans and Pets

Symptoms appear within 12 to 48 hours of urushiol's coming into contact with the skin and most commonly take the following form (both on animals and humans):

  • Blisters
  • Red patches
  • Swelling

In addition to the type of blister you're most familiar with, the rash can also take the curious form of a raised, straight line. The rash lasts for two or three weeks. Regardless of the appearance of these manifestations, they will be accompanied by an itch and can be painful.

You don't get the rash the first time you come into contact with poison ivy. Instead, most people (those allergic to urushiol) are sensitized to it during this initial contact. Future contacts increase that sensitivity until, finally, you're a prime candidate for developing the rash. That's why you'll hear some people marvel over the fact that, when kids, they touched poison ivy all the time and never got a rash, but that, as adults, they've "all of a sudden" lost their "immunity."

Gardening Considerations

Poison ivy could be invasive where it's an alien plant, but it's aggressive even where it's native. Poison Ivy can spread quickly, so if you find them near your garden, it could take over some of your plants and foliage.

Botanical Name Toxicodendron radicans
Common Name Poison ivy
Plant Type Deciduous, woody plant; can take the form of a shrub, climbing vine, or creeping vine
Mature Size Mature vines can climb 50 feet or more up a tree and develop a 6-inch diameter
Bloom Time Summer
Flower Color Off-white

Identification of Poison Ivy

Poison ivy's leaf is famously composed of three leaflets. But it's smart to learn about other ways to identify it (so that you don't accidentally touch it when it doesn't have leaves, for example) and how its appearance changes over time. Besides its distinctive leaf, poison ivy has small, off-white flowers, white berries, and "hairy" vines on older plants.

  • Small, off-white flowers
  • White berries
  • "Hairy" vines (on older plants)

How Poison Ivy Changes in the Course of a Year

The most obvious way in which poison ivy's appearance changes from season to season is in the look of its foliage:

  • Spring: various shades of red or orange
  • Summer: green
  • Fall: red, orange, or yellow (quite spectacular in some cases, as is also true of Toxicodendron vernix, known commonly as "poison sumac")
  • Winter: none, because the leaves will have dropped off by this time
baby poison ivy
Poison ivy in beginning stages. John / Flickr / CC by 2.0
Image of young leaves of poison ivy.
This is what the young leaves of poison ivy look like, while the plants are still fresh in spring. David Beaulieu
mature poison ivy
Bill Tanneberger / Flickr / CC by 2.0

Where It's Found

Poison ivy is native to the eastern United States and eastern Canada; therefore, by definition, it can't be considered invasive there, even though it spreads aggressively even in that region. But it could be invasive in regions to which it has been introduced. Poison ivy is not fussy about sun and soil conditions, which is one reason why it is such a successful plant.

How to Remove Poison Ivy

Poison ivy should be removed from areas near the garden so that you don't accidentally make contact with it while gardening, although it may take several tries to get rid of an established patch of poison ivy. It is possible to safely eradicate poison ivy, whether organically (manually) or with herbicides, but you must take extreme precautions. When working around poison ivy, it's especially important to wear gloves (wash them separately afterward from your other laundry) so that any residue you pick up isn’t transmitted to your food, your face, your pets, other people, or any other surfaces.