The most widespread of the three, poison ivy is found throughout most of North America, including all of the United States with the exception of California, Alaska, and Hawaii. Poison ivy can grow in many forms including a groundcover, shrub or a climbing vine. Poison ivy prefers “disturbed ground” so you can find it growing along the edge of your backyard, along paths, up trees and fences, and mixed in with your landscaping.
Poison oak is not as widespread as poison ivy, but to make things more interesting there are two species found in the United States, Eastern Poison Oak and Western Poison Oak. Don't let the terms confuse you though, the plants look the same. Poison oak has three leaflets like poison ivy, but they are scalloped and shaped like the leaves from an oak tree.
Unless you live in the swamp, it is very unlikely you will ever cross poison sumac in your yard. Found in the Eastern United States, poison sumac grows as a wooded shrub that may look like a small tree (grows up to 20 ft.) located in very wet areas like swamps and peat bogs.
Is it poison oak or is it poison ivy? Most people watch out for "leaves of three" but don't really know the difference. They do have in common the same rash-causing resin, called urushiol. Urushiol is found in all parts of the plants, even if the plant has died. Any interaction with the plant may cause your body to come in contact with urushiol.
Have you ever had a rash from poison ivy, oak or sumac and had no idea how such a thing could have happened? You backtrack through your last few days of events. It just doesn't make sense how you could have possibly come in contact with a poison plant. Well, you could be a victim of secondary contamination.
It's getting colder outside and a nice warm fire in the fireplace sounds good. You venture outside and grab some cut firewood and toss it in the fireplace. The only problem is there was a dead poison ivy vine wrapped around it. This could be very dangerous.
So who (or, what) is the culprit behind the spread of poison ivy rash? A highly concentrated, invisible oil called, urushiol. Urushiol, is the rash-causing oil found in all parts of poison ivy, poison oak, and poison sumac plants. Approximately 85% of the population experiences an allergic reaction to these noxious plants, and according to the National Institute of Occupational Health & Safety, 50 micrograms of urushiol is enough to cause a rash in 80-90% of adults. That is less than one grain of table salt!
Not sure what caused your poison ivy/oak rash? Many people know what a poison ivy. oak or sumac rash looks and feels like, but do not really understand why the plants cause such a painful, itchy rash. Once you understand how the plants work, it is easier to avoid a rash.