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6 Pesky Poisonous Plants to Watch Out For

Wednesday, July 10, 2019 3:23 PM
Tags: allergy,poison

If you’re heading out into the great outdoors, make sure you’re aware of which plants you come in contact with or brush up against. Summertime may bring warmer weather, but it’s also the time of the year when wild plants are known for sprouting up. Some are harder to recognize than others, and some can cause severe pain.

Jennifer S. Kim, MD, Allergist at NorthShore, shares what you should do if you come in contact with these plants:


Wild Parsnip:

Wild Parsnip

Don’t pick these! The pretty and tiny yellow flowers on this plant are deceiving. Found throughout North America, contact with the sap of this plant can cause a painful light-sensitive rash that can cause blistering and scarring. The sap can cause blindness if it gets into the eye.

  • Where it grows: Prairies, open fields and bike paths.
  • Appearance: Non-native, yellow weeds.
  • Symptoms: Can cause inflammation and a burning sensation followed by blisters and welts appearing later and overnight.
  • Treatment: Shower immediately and wash all clothing after contact. Stay out of the sun and call your doctor, who may recommend topical steroids. Milder symptoms may be treated with hydrocortisone.

Giant Hogweed:

Giant Hogweed

  • Where it grows: New York, Pennsylvania, Ohio, Maryland, Oregon, Washington, Michigan, Virginia, Vermont, New Hampshire and Maine.
  • Appearance: A noxious weed that features clusters of white flowers that can reach up to 14 feet tall. Its stems are green with purple blotches and white hairs.
  • Symptoms: The toxic chemicals in this plant are known as photosensitizing furanocoumarins. When they come in contact with the skin and light, a toxic reaction can happen within 15 minutes and continue to get worse with dark painful blisters within 48 hours.

Poison Ivy:

Poisonous Plants

Poison ivy is the only one of the poisonous plants on this list that has three leaves, one on each side and one in the center. They’re shiny with smooth or slightly notched edges. Poison oak is similar, but the leaves are larger and more rounded.

  • Where it grows: In all U.S. states except Alaska, Oregon, Hawaii, California. Open fields, forest preserves and on roadsides. It can also be found in more common areas such as parks and backyards.
  • Appearance: The color of poison ivy is different each season. In the summer, leaves are usually green. In the fall, they change color with the surrounding trees. Can grow up to four feet tall as groundcover or climbing vine. The plant’s berries are a grayish-white color.

Poison Oak:

Poison Oak

When the leaves of this plant are bruised or damaged, it releases an oil called “urushiol” which can cause dermatitis, and uncomfortable allergic rash.

  • Where it grows: Along the Pacific Coast and Atlantic Coast. Rare in Midwest. 
  • Appearance: Dense shrub in the sun or climbing vine in the shade and leaves are slightly more jagged. The plant grows up to six feet tall, with green, yellow or white berries, and does a great job camouflaging itself to blend in with the surrounding plants.
  • Symptoms: Itchy red rash with bumps or blisters

Poison Sumac:

Poison Sumac

  • Where it grows: Wet, flooded or swamp-like areas near the Mississippi River and boggy areas of the southeast. Much less common than poison ivy or oak.
  • Appearance: Grows as a shrub or a small tree. Typically, there are seven to 13 leaflets per stem, veins are always red, with the leaves having pointy tips. The fruit is a small white or gray berry.

Stinging Nettle:

Stinging Nettle

More benign than others on this list, you should still watch out for this one if handled incorrectly. Interestingly, despite the danger of touching this plant, once cooked it can be healthy to eat.

  • Appearance: These plants are three to four feet high and are found in large clusters. They feature jagged, deep green leaves and clusters of greenish-white flowers. The stems are covered with stinging hairs.
  • Symptoms: When brushed up against bare skin, it can cause a stinging, burning sensation.

For Poison Ivy, Oak and Sumac symptoms and treatment are the same:

  • Symptoms: It takes about 4-96 hours for the reaction to take place, and the symptoms you may experience include redness, itching, difficulty breathing and blisters. New lesions can occur up to 21 days after exposure, which can give the impression that the poison ivy is spreading. Touching the blisters or the fluid inside the blisters will not spread the rash.
  • Treatment:  Remove any contaminated clothing and gently wash the skin with mild soap and water as soon as possible, including under fingernails. Try oatmeal baths and cool compresses. See your doctor if the rash is extensive or affects your face and/or genitals.