Every year in the United States, there are more than 1 billion upper respiratory tract infections and colds. In addition, 5 to 25 percent of Americans get the flu, which results in 200,000 hospitalizations and anywhere from 20,000 to 36,000 deaths, depending on the year.
When you are otherwise healthy and get sick, your immune system pumps out protein molecules called cytokines, which help battle the virus and lead to many of the symptoms you experience—sneezing, coughing, a runny nose, and puffy eyes. It's the body's immune response to the virus that makes you feel so bad, not the virus itself. That's why it makes no sense when supplements claim they can "boost" your immune system. It's already boosted! (How Healthy Is Your Immune System?)
If you have symptoms that come on gradually and are primarily above the neck—sneezing, sore throat, watery or itchy eyes—you probably have a cold. If you have symptoms that come on quickly, are severe, and are above and below the neck—fever (a key symptom of the flu), shivering, sweating, achy muscles and limbs—you've probably caught the flu. I like to say: "One is a nuisance and the other is a knockout."
Here's what works: