Poison ivy is a common North American plant that causes an itchy, blistering rash when you touch it. The plant protects itself with an oil called urushiol that sticks to your skin, clothes, and even pet fur. Within hours or days, red bumps appear that itch intensely. The rash can show up on new areas of skin if the oil spreads.

You can recognize poison ivy by its clusters of three pointed leaves, which is why people say, “Leaves of three, let it be.” The leaves are shiny and can be reddish in spring, green in summer, and yellow or orange in fall. The plant grows as a low shrub or climbing vine, often along trails, fences, or at the edges of woods.

If you touch poison ivy, wash the area immediately with soap and cool water to remove the oil before the rash starts. The oil can remain active on unwashed clothes, tools, or soccer balls for months, so anything that touched the plant needs cleaning. Even dead poison ivy plants contain the oil and can cause a rash.

The best strategy is learning to identify poison ivy and avoiding it completely. Once you know what those three-leaf clusters look like, you'll spot them everywhere and can steer clear. About 85% of people are allergic to poison ivy's oil, so chances are high that touching it will make for a miserable, itchy week.