As the temperature rises, so do your opportunities to commune with nature. Do not let poison ivy ruin your plans!

One beautiful summer day, Joanna recruited her two young children to help her work in the backyard. After working in the vegetable garden, she and her kids turned their attention to the patch of weeds growing at the back of the yard and along one side of the house.

The next morning, Johanna awoke to find a slightly uncomfortable rash erupting on her arms and lower legs. So did her daughters. Over the course of the day, their rashes grew progressively worse. By Monday morning the three were scratching furiously. By mid-afternoon, they were in the doctor's office. The diagnosis? Poison ivy.

Poison ivy,oak, and sumac grow almost anywhere—deep in the woods, at the local park, in the sand dunes at the beach, or in your yard.

The culprit behind the extremely uncomfortable allergic skin rash of poison ivy, oak, and sumac is urushiol (pronounced "you-ROO-shee-ol"), an oily substance found in every part of the plant except the pollen. Upon contact with the skin, urushiol is almost immediately absorbed. If not removed quickly—within about 10 minutes—an allergic reaction (in most people) begins with redness and swelling followed by extreme itchiness, and then by blisters (filled with a yellowish fluid) that can break open, causing crusting and scaling.

Most people develop a full-blown rash within 12-72 hours of exposure. But, depending on the amount of exposure others may find themselves with their first rash after 7-10 days. Although the itching and swelling can be treated and controlled, there is no cure per se for the rash itself, which usually takes 1-3 weeks to run its course.