How Poison Ivy Works

According to the American Academy of Dermatology, an estimated 10 to 50 million people in this country have an allergic reaction to poison ivy each year [ref]. Poison ivy is often very difficult to spot. It closely resembles several other common garden plants, and can also blend in with other plants and weeds. But if you come into contact with it, you'll soon know by the itchy, blistery rash that… » Full Story on HowStuffWorks