If you already have a blister, try the trick used by distance runners: Goop Vaseline on the trouble spot, put on your socks and shoes, and hit the road. Your sock may be gooey, but the Vaseline will reduce friction and the blister won't irritate you. If the blister is a mild one, a Band-Aid or a piece of moleskin or second-skin (without Vaseline) should provide enough protection for you to continue running, biking or hiking.

Once a blister forms, resist the urge to pop it. "That's just normal body fluid inside, and if you pop it, it's more likely to get infected," says John Wolf, M.D., chairman of dermatology at Baylor College of Medicine. If it pops on its own, keep it clean and apply antibiotic cream. Should an infection develop, get to a doctor right away: Because they remove a large area of protective skin, blisters run a higher risk of developing bad infections than minor cuts and scrapes; if a blister gets infected, see a doctor immediately.

Plant punch: Poison ivy, oak and sumac
Enemies to hikers and mountain bikers, these plants cause nasty rashes that can last for two weeks. They thrive in summertime, growing almost everywhere in the States except Hawaii, Nevada and Alaska (poison ivy doesn't grow in California, and sumac is found only in the Eastern states). Because they vary so much in size and color depending on where in the country they're growing, poison oak and ivy can be hard to identify. So it's best to simply avoid any shrub or vine with three leaves on one stem. (Remember the old saw, "Leaves of three, let them be.") Poison sumac has paired, pointed leaves, sometimes with greenish-white berries. A new over-the-counter cream called IvyBlock 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.