The dangers of touching or eating a poisonous plant range from mild irritation all the way to death.
In the U.S. the hazardous plant you're most likely to come into contact with is poison ivy—or its cousins in the genus Toxicodendron, poison oak and poison sumac. They won't cause serious illness, but their sap oil can trigger an allergic skin reaction, according to the U.S. Centers for Disease Control and Prevention (CDC).
Toxicodendron plants are found in every state of the continental U.S. and are "strong and hard to get rid of," states MedlinePlus, a National Library of Medicine website. They thrive in sunny and hot areas and do not survive well above 5,000 feet, in deserts or in rainforests.
Below, botanical and poisons experts explain how to spot poison ivy, what to do if you touch it and how to treat a rash.
What Does Poison Ivy Look Like? How to Identify It
Poison ivy, or Toxicodendron radicans, is a climbing vine and less commonly a free-standing shrub, according to botanist Susan Pell, deputy executive director of the U.S. Botanic Garden.
Kelly Johnson-Arbor, co-medical director of the National Capital Poison Center, told Newsweek: "Poison ivy can be difficult to identify as it is easily confusable with other common plants."
If you're not sure whether the plant in front of you is poison ivy, look for these features:
- Leaves with three leaflets each—not five like the leaves of the somewhat similar-looking Virginia creeper (Parthenocissus quinquefolia). Poison ivy vines have solid green, pointed glossy leaves that are arranged in groups of three.
- Leaves alternating on the stem, not opposite each other like the leaves of the box elder (Acer negundo).
- Poison ivy does not have prickles—unlike blackberry and raspberry plants.
- Damaged parts of the plant usually have black spots or black sap.
- The leaves turn yellow, orange and red in the fall.
- The flowers and fruits are cream-colored. Poison ivy vines may produce yellow or green flowers and white berries in different seasons.
Poison oak is a shrub with three leaves. It's mostly found on the west coast, according to MedlinePlus.
Poison sumac is a woody shrub found in abundance along the Mississippi River. Each stem has seven to 13 leaves arranged in pairs.
How to Get Rid of Poison Ivy Permanently
"It's best to avoid poison ivy as much as possible," said Johnson-Arbor. To eradicate it from your garden, you'll likely need a chemical herbicide.
"People may also choose to hire a professional to manually remove poison ivy plants from their property, but this must be done with care to avoid physical contact with the plant," she added.
The manual removal of the plants can be successful, Pell told Newsweek, but it usually takes several years and a lot of persistent work. "A faster solution is to apply an effective herbicide directly to the poison ivy."
For very large stems, cut across the whole stem to detach the higher climbing portions from the roots. Then drill a few holes in the stem and fill them with herbicide to kill the roots, she advised.
The CDC cautions against burning poison ivy, because the smoke can cause lung irritation.
What Does Poison Ivy Rash Look Like?
Poison ivy rash usually develops within a day or two of exposure and is characterized by "severe itching, redness and streaking that may develop into painful blisters," said Johnson-Arbor.
The severity of the rash varies depending on the person and level of exposure. You might see small reddish bumps, red, inflamed skin or even large blisters filled with clear fluid, Pell said.
How Does Poison Ivy Spread? How Long Is It Contagious?
The rash results from direct contact with urushiol, an oily liquid produced by poison ivy and other members of the plant's family—which is also known as the cashew family. There are about 800 known species in the family, including mangos, pistachios, poison oak and poison sumac, Pell said.
Around three-quarters of the population is "sensitive to the toxic effects of poison ivy," according to Johnson-Arbor, and the urushiol is present in nearly every part of the plant.
Pell explains that people can also come into contact with urushiol in these ways:
- It can stay on tools, clothing and other items for years. However, it is easily washed off to make these items safe to touch again.
- Many come into contact with urushiol via their pets, who don't usually develop a rash but can carry urushiol on their fur.
- Smoke from burning poison ivy can cause severe allergic reactions.
Johnson-Arbor said: "The rash associated with poison ivy is not contagious. However, it's important to wash off skin with water as soon as possible after an exposure to poison ivy, as any remaining urushiol on the skin can easily transfer to other body parts or other people and cause additional rashes and blistering."
Once an animal, tool or clothing item has been washed, "you can no longer get a poison ivy rash from coming in contact with them. This is true of contact with people and other impacted animals, no matter how nasty their rash is," Pell added.
The CDC recommends that you rinse any exposed skin with water and either rubbing alcohol, poison plant wash or a degreasing soap (such as dishwashing soap) or detergent. You should also scrub under your nails with a brush. "Rinse frequently so that wash solutions do not dry on the skin and further spread the urushiol," it added.
How to Treat Poison Ivy Rash and How Long It Lasts
The rash can last days or weeks, Johnson-Arbor said. Pell added that the duration "varies enormously" but is typically one to three weeks.
To treat the rash, Johnson-Arbor recommends:
- Applying wet compresses or soaking the affected areas in cool water.
- Applying over-the-counter corticosteroid medication to intact skin (not blistered areas).
- Taking oral antihistamines (such as diphenhydramine) to help with the itching. Oatmeal baths may also relieve the itching, according to the CDC.
- In severe cases, patients may require oral corticosteroids (such as prednisone).
While minor cases can be treated with over-the-counter anti-inflammatory, analgesic and antihistamine medications, anyone with a severe rash or other health condition should seek advice from their doctor, Pell said.
If you suspect a poisoning, contact the National Capital Poison Center at 1-800-222-1222 (available 24 hours a day) or visit poison.org.
