What is poison oak?
The term “poison oak” can refer to one of two similar plants: Toxicodendron Diversilobum, and Toxicodendron Pubescens. Both produce an oil called urushiol, which is a skin irritant causing the majority of people who come into contact with it to experience an allergic reaction known as urushiol-induced contact dermatitis. Most often, this itchy, burning, bumpy rash is known as “poison oak rash”. Despite this name, the term “poison-oak” (with the hyphen) is often used in order to clearly indicate that these plants are not actually varieties of oak at all! Similarly, “poison-ivy” is not really an ivy. Nevertheless, the names “poison oak” and “poison ivy” are the ones that are most commonly used when referring to these plants.
Toxicodendron Pubescens, or “Atlantic poison-oak”, is native to the Southeastern states of the US, and can be found as far west as Oklahoma and Texas. An erect shrub that grows in thickets and forests, and also in dry or sandy fields, Atlantic poison-oak can grow to about 3 feet tall (a meter), and varies in appearance depending on the time of year – green, but turning yellow or orange in the fall. The leaves are alternate on the stem, in bunches of three, and normally hairy. The plant gets the name “poison oak” because the leaves usually resemble white oak leaves.
Toxicodendron Diversilobum, or “Western/Pacific poison-oak”, is found on the Pacific coast of Canada and the US. It's more like poison ivy in its diversity, and can grow in several different forms depending on its habitat, putting out creeping vines in order to spread. The leaves are very like the Atlantic poison oak variety, although somewhat more glossy than true oak leaves. It takes the form of a dense shrub (in areas of open exposure to sunlight) or a climbing vine (where there is less light) or single stems (in grassland), and is really common in California in particular, often found in oak woodlands and forests of Douglas firs. You're also likely to see it in mountain areas and near to waterfalls.
Poison oak can have some nasty effects on humans, the majority of whom are allergic to the urushiol it contains. This oil is very easily transferred by touch, and when it is absorbed by the skin it will cause the aforementioned itchy rash, and often painful blisters and burning sensations as well. Although only very serious cases of poison oak require hospitalization, the experience is often very unpleasant for the sufferer. Various natural and over-the-counter remedies are available, but these serve more to ease the symptoms rather than as an outright cure. The rash usually takes at least a few weeks to completely heal. That's why prevention is the best approach – it's wise to know what poison oak is, where it grows, how to identify it, and what to do if you accidentally come into contact with it. Ignorance can lead to a great deal of discomfort!
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