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 native plants that cause an allergic skin reaction—poison ivy, poison oak, and poison sumac.

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.

Plant Identification

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.

Poison Ivy

• 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

Poison Oak

• 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

Poison Sumac

• Woody shrub that has stems that contain 7-13 leaves arranged in pairs
• May have glossy, pale yellow, or cream-colored berries

http://www.cdc.gov/niosh/topics/plants/