Poisonous plants cause the most common allergic reactions to the skin, affecting as many as 50 million Americans each year, according to the American Skin Association.
University of Alabama at Birmingham associate professor of Emergency Medicine, Walter Schrading, M.D., says it is important people are able to identify poisonous plants, prevent an allergic reaction and treat skin irritations after contact.
Identification of poisonous plants
The three most common types of poisonous plants are poison ivy, poison oak and poison sumac. All three plants produce the same resin called urushiol, which helps the plant retain water. The colorless resin exists on the stems and leaves of these plants, causing toxic effects within 24-48 hours of coming in contact with skin.
Poison ivy is a three-leaf plant that is found on the East Coast in moist, shady areas. It is a vine plant that often grows up trees.
Similarly, poison oak is a three-leaf plant found on the West Coast and some Southern states, growing in shrubs. The plant may have clusters of green-yellow or white berries on the vine-like plant.
Poison sumac is found in wet, marshy regions around riverbanks and looks like a small tree or shrub, sometimes growing 15 feet tall or more. The stem has seven to 13 smooth, oval leaves that are arranged in pairs.
“The adage, ‘Leaves of three, let me be,’ is a good one stick by,” Schrading said. “When working in the yard or exploring outdoors, it is important to be aware of your surroundings and the plants that you come in contact with.”
Virginia creeper is often mistaken for poison ivy. The imposter plant looks like poison ivy, but has five leaves. Often, the two plants grow together. Although it is not as allergenic as poison ivy, raphides, the sap of Virginia creeper, can cause skin irritation and blisters in sensitive people when it punctures the skin.
Prevention of an allergic reaction
Poisonous plants are a common cause for skin rashes. Urushiol is found on the poisonous plants year-round, even when the plants are brown and not fully grown. Precaution should be taken even in the fall and winter months.
“Prevention is key when you are outdoors,” Schrading said. “If you are in an area that contains weeds or overgrowth, it is best to take precautions to protect your skin from interacting with the resin that comes off the plants.”
A few precautions to take:
• When outdoors in wooded areas, wear long pants and long sleeves to avoid contact with poisonous plants.
• If you are gardening and suspect poisonous plants in the area, use gloves to extract the plant.
• Use Ivy Block, an over-the-counter topical containing Bentoquatam, which protects skin from urushiol. It should be applied every four hours.
The severity of the rash will depend on the person and his or her allergic reaction. There is a group of patients who have a genetic predisposition to an extreme reaction based on their heredity.
Contact dermatitis is the skin rash caused from exposure to poisonous plants. It is a red, linear rash that burns or itches, and oddly enough, some symptoms may not occur until 10-14 days after contact. Severe symptoms will include small bubbles forming on the skin, swelling around the contact dermatitis, skin leaks and skin crusts.
Typically, the extremities — or legs and arms — come in contact with urushiol. The rash can spread to areas that may not have been exposed due to touching the plant, like touching or scratching the ears, nose, etc. If the resin is on clothing, it can be transferred if bare skin comes in contact with the clothing item.
Pets can also transfer the resin from the plant to humans. It rarely affects pets, as their fur acts as a protective barrier.
“If a dog brushes up against a plant, then you pet the dog, you come in contact with urushiol and could have an allergic reaction,” Schrading said. “If you have an unexplained rash, this could be the culprit.”
Treatment for skin contacted by urushiol
More than 85 percent of the population will have some type of allergic reaction when their skin comes in contact with urushiol. Ten to 15 percent of those people will have a severe reaction to the poisonous plants.
“When people have contact dermatitis, they tend to scratch the rash, damaging the skin. This becomes a vicious cycle and keeps the skin from healing fully,” Schrading explained.
If you suspect that you have come in contact with a poisonous plant, rinse the area with soap and water or rubbing alcohol as quickly as possible. If using rubbing alcohol on children, use sparingly.
Once you have contact dermatitis, it will take one to two weeks minimum to heal. Here are a few options for treatment at home:
• Use a topical cortisol steroid like hydrocortisone, available over the counter, to treat the rash.
• Calamine lotion serves as a soothing agent and promotes drying of the skin to heal the rash.
• Aluminum acetate paired with a cool compress provides relief during the blistering stage.
• Soaking for 15-20 minutes in an oatmeal bath can soothe the itching sensation.
If the allergic reaction spreads to a lot of the body and swelling of the face and eyes is experienced, a physician can prescribe an oral steroid to help promote healing. Seek medical treatment if the allergic reaction is on the face, as cortisol may not be safe to put on the face.
Known for its innovative and interdisciplinary approach to education at both the graduate and undergraduate levels, the University of Alabama at Birmingham is the state of Alabama’s largest employer and an internationally renowned research university and academic medical center; its professional schools and specialty patient-care programs are consistently ranked among the nation’s top 50. UAB’s Center for Clinical and Translational Science is advancing innovative discoveries for better health as a two-time recipient of the prestigious Center for Translational Science Award. Find more information at www.uab.edu and www.uabmedicine.org.