To tell whether you have a cold or just allergies, simply blow your nose. "If the discharge is runny and clear, chances are it's allergies," says Dean Mitchell, an allergist in New York City. "If it's yellowish or green, you've most likely caught a cold." Both colds and allergies give you a sore throat, a dull headache, and an overall crummy feeling, according to Mitchell, but itchy eyes, hives, and wheezing go along with allergies, whereas body aches and swollen glands are signs of a cold. "A cold will last 7 to 10 days," says Russell Roby, an allergist in Austin, Texas. "If your symptoms stick around for two to three weeks, you're either allergic or have come down with something else, like the flu or an infection." The good news is that you no longer have to be poked with dozens of needles to be tested for allergies. "Now we do an immunocap blood test," Mitchell says — one prick and your doctor can determine exactly what you are allergic to. "It's one-stop shopping."