The mucous is sent to the stomach, where the acids it produces destroy the invaders.
Because of that, keeping nasal passages moist is an important step.
"Humidifiers can be really helpful," said Haller.
Additionally, in dry air, particles like the flu virus can stay airborne longer. By moistening the air, the water droplets will adhere to the particles, sending them downward.
A study done at the Mount Sinai School of Medicine last year showed that, in gerbils at least, relative humidity and temperature had a lot to do with how much the influenza virus spread.
Haller recommends using a saline solution as well to keep the nasal passages moist. (For a video demonstration of how to do this, click here.)
"Since it's just saltwater … you can do it every couple hours if you need to," said Haller.
Even ensuring that you're drinking enough water, Haller said, can help keep the body moist enough to protect against the flu.
Almost always a good idea anyhow, exercise can help you avoid the flu as well.
"Exercise can help boost the immune system," said Fryhofer.
The increased circulation from exercise gets white blood cells moving around the body to help fight off infections.
But exercise may not do much once you have the flu. While people who feel up to it can exercise, as Dr. Lisa Bernstein, an assistant professor of medicine at Emory, explains, most are too tired to exercise when they have the flu.
Keeping your immune system in top shape involves eating right, exercising and getting enough shut-eye.
And flu season is no exception. Sleeping enough has the added benefit that it cannot only help you avoid the flu, but if you do get it, you may not have it as long.
"Get plenty of rest, so if you do get sick, you can get over it more quickly," said Fryhofer.
Because hand-to-hand contact is one of the best ways the flu has of moving from person to person, you may be inclined to avoid shaking hands altogether, especially given the hand hygiene of many people.
If that is your mindset, Fryhofer recommends having something in your hands so that you can greet without offending.
But because that won't always be an option, she advises simply being mindful when you do shake hands that you clean them -- either by washing or with a gel, shortly afterward.
"You have to know the person," Fryhofer said.
As many studies have shown, not everyone is going to go through the same effort to keep their hands clean, but while it may mean some extra caution on your part, there's probably little you can do about that.
"The main thing is just making sure your own hands are clean," said Haller.
Rubbing your eyes or nose and chewing your nails are all ways your hands can come in contact with your eyes, nose and mouth -- and all of them should be avoided.
Our hands are constantly picking up germs, and giving those germs a pathway into our body is how they make us sick.
"Generally, at some point, our hand goes to our nose, whether we like it or not, and that can transmit flu viruses from one person to another," said Haller.
Keeping your hands clean is one way to prevent the problem, but keeping them from your face may just be a matter of willpower.
It isn't the food as much as how you're getting it into your mouth.