As many of us have found out the hard way, poison oak and poison ivy can cause nasty rashes that can last for up to two weeks. These pernicious plants thrive in summertime; in the Bay Area, poison oak seems to be the biggest threat. Sometimes it’s hard to spot these plants on a hike or mountain bike ride. To be safe, it's best to simply avoid any shrub or vine with three leaves on one stem. ("Leaves of three, let them be.") Also, there’s an over-the-counter cream called IvyBlock that helps keep the plant oils from being absorbed by the skin, so it's worth a try if you know you'll be near these plants. If you think you touched either oak, ivy or sumac, do not touch your face, other body parts or even other people because you could spread the plant oils that cause the rash. Go home and scrub all exposed areas with soap and warm water; then wash your clothes. If you develop an itchy rash, treat yourself with cool, wet compresses and an over-the-counter hydrocortisone cream to combat swelling and itch. If it’s a significant case, as in your whole body is rash or it gets on your face and eyes, get thee to a doctor who can prescribe a more potent remedy.