Prevention is hands-down the best medicine, says Michael Benninger, M.D., otolaryngology chief at Henry Ford Hospital in Detroit. If you've ever had swimmer's ear before, you're prone to get it again. "So make a 50-50 mixture of rubbing alcohol and white vinegar, and put a few drops in each ear after you swim," advises Benninger. The rubbing alcohol is drying, and the acidic vinegar creates a bacteria-hostile environment. If an infection takes hold anyway, the alcohol/vinegar mix may abort it if you catch it early. But chances are you'll need to get prescription antibiotic drops. "If it's painful, draining, and/or your hearing has decreased, get medical attention," says Benninger.

Overuse injuries
"As soon as spring comes, we see more tendinitis, stress fractures, muscle pulls, and other overuse injuries," says Lewis Maharam, M.D., president of the New York chapter of the American College of Sports Medicine. "If you haven't kept up training over the winter, make sure you ease into a sport, don't jump in." The more time you spend stretching and strength training right now, the less likely you'll be sidelined with an injury come July.

Blisters
Most blisters result from poorly fitting shoes or from sweat-soaked socks, when the wet, heavy fabric rubs against your skin. "Wear socks made of [fabrics like] CoolMax or SmartWool," says Christine Wells. "They can prevent blisters because they don't absorb as much sweat."