Vitamin C can’t prevent the crud, but it might make it go away faster. Studies show that taking vitamin C supplements just before cold symptoms start (like when you get that familiar tickle in your throat) can keep them from sticking around. Once your cold is full-blown, though, it’s too late for vitamin C to help.

Doctors agree: The best way to protect yourself is to get the flu vaccine every year. You should also do your best to avoid germs by washing your hands and staying away from people who are sick. But recent studies show the shot can lower your chances of getting the flu by about 40% to 60%, depending on how well the vaccine matches the flu viruses that are going around.

Of these three, only zinc has research showing that it can shorten a cold. Scientists haven’t been able to prove that probiotics or echinacea make much difference in prevention or treatment. Zinc lozenges, tablets, or syrup can make your cold shorter and less horrible.

If you have a choice, always go for the sink and suds. Sanitizer is good in a pinch, but it doesn’t remove or kill all types of germs -- hand washing is better at that. If you do use sanitizer, choose one with at least 60% alcohol for best results.

It’s true -- the doorknob your sneezing friend just touched can infect you up to 8 hours later. That’s why it’s important to wash your hands often. For the best protection, wipe down surfaces when you can, and keep your fingers away from your eyes, nose, and mouth, too.