It’s that time of year again. You’re out working in the garden, or hiking through the woods, looking for fossils (of course!). The New York Times had an article about poison ivy a few weeks ago. Hopefully, it will help you identify it, so you don’t have to endure a few weeks of intense itching…

Well over half of the human population is sensitive to poison ivy, poison oak or poison sumac. Rashes usually peak in early summer, and tens of thousands of people in the United States go to the emergency room every year as a result. Even if you’ve gone your whole life without a sensitivity, you can develop an allergy at any point.

Your best bet for staying rash-free is leaving plant life alone. But when you can’t avoid it, it’s helpful to know the characteristics of poison oak and ivy. A good rule of thumb is “leaves of three, let it be.” Leaf shape, size and color are less helpful, since they are notoriously varied in these plants. Another important tip: The entire plant, from root to leaf, contains the allergenic oil urushiol.