Many native and exotic plants are poisonous to humans when ingested or if there is skin contact with plant chemicals. However, the most common problems with poisonous plants arise from contact with the sap oil of several ever-present native plants that cause an allergic skin reaction—poison ivy, poison oak, and poison sumac.
Poison ivy, poison oak, and poison sumac release an oil, urushiol, when the leaf or other plant parts are bruised, damaged, or burned. When the oil gets on the skin an allergic reaction, referred to as contact dermatitis, occurs in most exposed people as an itchy red rash with bumps or blisters. When exposed to 50 micrograms of urushiol, an amount that is less than one grain of table salt, 80 to 90 percent of adults will develop a rash. The rash, depending upon where it occurs and how broadly it is spread, may significantly impede or prevent a person from working. Although over-the-counter topical medications may relieve symptoms for most people, immediate medical attention may be required for severe reactions, particularly when exposed to the smoke from burning these poisonous plants. Burning these poisonous plants can be very dangerous because the allergens can be inhaled, causing lung irritation.
Outdoor workers may be exposed to poisonous plants. Outdoor workers at risk include farmers, foresters, landscapers, groundskeepers, gardeners, painters, roofers, pavers, construction workers, laborers, mechanics, and any other workers who spend time outside. Forestry workers and firefighters who battle forest fires are at additional risk because they could potentially develop rashes and lung irritation from contact with damaged or burning poisonous plants. It is important for employers to train their workers about their risk of exposure to poisonous plants, how they can prevent exposures and protect themselves, and what they should do if they come in contact with these plants.
One or more of the most common poisonous plant species are found throughout the United States (except Alaska and Hawaii). These plants can be found in forests, fields, wetlands and along streams, road sides, and even in urban environments, such as, parks and backyards.
Across the United States, except California, Alaska, and Hawaii
Primarily the Southeast and West Coast
Abundant along the Mississippi River and boggy areas of the Southeast
The old saying "Leaves of three, Let it be!" is a helpful reminder for identifying poison ivy and oak, but not poison sumac which usually has clusters of 7-13 leaves. Even poison ivy and poison oak may have more than three leaves and their form may vary greatly depending upon the exact species encountered, the local environment, and the season. Being able to identify local varieties of these poisonous plants throughout the seasons and differentiating them from common nonpoisonous look-a-likes are the major keys to avoiding exposure.
- Eastern poison ivy is typically a hairy, ropelike vine with three shiny green (or red in the fall) leaves budding from one small stem
- Western poison ivy is typically a low shrub with three leaves that does not form a climbing vine
- May have yellow or green flowers and white to green-yellow or amber berries
- Typically a shrub with leaves of three, similar to poison ivy
- Pacific poison oak may be vine-like
- May have yellow or green flowers and clusters of green-yellow or white berries
- Woody shrub that has stems that contain 7-13 leaves arranged in pairs
- May have glossy, pale yellow, or cream-colored berries
Workers may become exposed to urushiol through:
- Direct contact with the plant
- Indirect contact, such as touching tools, livestock, or clothing that have urushiol on them
- Inhalation of particles containing urushiol from burning plants
Signs or symptoms associated with dermal contact with poisonous plants may include:
- Red rash within a few days of contact
- Possible bumps, patches, streaking, or weeping blisters (blister fluids are not contagious)
Employers should protect their workers from poisonous plants by training them about:
- Their risk of exposure to poisonous plants
- How to identify poisonous plants
- How to prevent exposure to poisonous plants
- What they should do if they are exposed to poisonous plants
Workers can prevent contact with poisonous plants by taking these steps:
- Wear long sleeves, long pants, boots, and gloves.
- Wash exposed clothing separately in hot water with detergent.
- Barrier skin creams, such as a lotion containing bentoquatum, may offer some protection before contact.
- Barrier creams should be washed off and reapplied twice a day.
- After use, clean tools with rubbing alcohol (isopropanol or isopropyl alcohol) or soap and lots of water. Urushiol can remain active on the surface of objects for up to 5 years.
- Wear disposable gloves during this process.
- Do not burn plants that may be poison ivy, poison oak, or poison sumac.
- Inhaling smoke from burning plants can cause severe allergic respiratory problems.
Employers should prevent workers from being exposed to burning poisonous plants whenever possible. However, when exposure to burning poisonous plants is unavoidable, employers should provide workers with:
- A NIOSH-certified half-face piece particulate respirator rated R–95, P–95, or better. This recommendation does NOT apply to wildland firefighters. Firefighters may require a higher level of respiratory protection to protect against possible exposure to combustion products.
- These respirators should protect against exposure to burning poisonous plants, but will not protect against all possible combustion products in smoke, such as carbon monoxide.
- Respirators must be worn correctly and consistently throughout the time they are used.
- For respirators to be effective there must be a tight seal between the user’s face and the respirator.
- Respirators must be used in the context of a written comprehensive respiratory protection program (see OSHA Respiratory Protection standard 29 CFR 1910.134 ).
Workers who have come in contact with poisonous plants should:
- Immediately rinse skin with rubbing alcohol, specialized poison plant washes, degreasing soap (such as dishwashing soap) or detergent, and lots of water.
- Rinse frequently so that wash solutions do not dry on the skin and further spread the urushiol.
- Scrub under nails with a brush.
- Apply wet compresses, calamine lotion, or hydrocortisone cream to the skin to reduce itching and blistering.
- Follow the directions on any creams and lotions. Do not apply to broken skin, such as open blisters.
- Oatmeal baths may relieve itching.
- An antihistamine such as diphenhydramine (Benadryl) can be taken to help relieve itching.
- Follow directions on the package.
- Drowsiness may occur.
- If children come in contact with work clothing contaminated with urushiol, a pediatrician should be contacted to determine appropriate dosage.
- In severe cases or if the rash is on the face or genitals, seek professional medical attention.
- Call 911 or go to a hospital emergency room if the worker is suffering a severe allergic reaction, such as swelling or difficulty breathing, or has had a severe reaction in the past.
- Page last reviewed: July 24, 2015
- Page last updated: May 20, 2016
- Content source:
- National Institute for Occupational Safety and Health Education and Information Division