Poison Ivy, Poison Oak, and Poison Sumac. Do you know which is which? With summer in full swing and these poisonous plants as hardy as ever, it pays to know. A good rule of thumb is ‘leaves of three, leave it be’ but a lot of plants carry three leaves, and what if they don’t follow the rule?


Within 12 to 72 hours of touching any one of these plants, you could develop a very uncomfortable, itchy red rash. So which ones which?


A: Poison Oak. Like its counterpart ivy, these poisonous leaves also cluster in sets of three. The edges of the solid green leaves are reminiscent of an oak tree. Poison oak is most often seen in shrub form, but it can also grow as a vine.


B. Poison Ivy. The trademarks of this plant are its solid green, pointed leaves that hang from the stem in groups of three. It grows as both a vine and a shrub. The look of poison ivy can change with the seasons. It produces yellow-green flowers in the spring and its green leaves can change to yellow and red in autumn.


C. Poison Sumac. This rash-producer thrives in the water. It’s usually found in swampy or boggy areas where it grows as small tree or tall shrub. Poison sumac leaves can have black or brownish-black spots. The leaf stems contain seven to thirteen leaflets.




Urushiol is the oily poison contained in the leaves of these plants. It can take only a single nanogram (a billionth of a gram) to cause a rash. The oil can stay active for 1-5 years on any surface including dead plants.




Poison Ivy rash is contagious.

Truth: Rubbing the rashes won’t spread poison ivy to other parts of your body (or to another person). You spread the rash only if urushiol oil has been left on your hands.


I’ve been in poison ivy many times and never broken out. I’m immune.

Not necessarily true. Upwards of 90% of people are allergic to urushiol oil, it’s a matter of time and exposure. The more times you are exposed to urushiol, the more likely it is that you will break out with an allergic rash. For the first time sufferer, it generally takes longer for the rash to show up – generally in 7 to 10 days.


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