The average American gets three colds a year, each lasting for nine to 14 miserable days, so it's no surprise that we spend billions of dollars on over-the-counter cold and flu remedies annually. Turns out that by and large, we're wasting our money. Evidence suggests that few remedies—herbal, over-the-counter, or homeopathic—are likely to influence the course of a cold or the flu. That said, some do work.

Zinc
Does it work? Maybe. Some evidence suggests that zinc lozenges (like Zicam and Cold-Eeze) may ease symptoms and shorten the duration of the common cold, but most studies are small and don't provide "robust" evidence of benefit, says Joy P. Alonzo, Pharm.D., assistant professor of pharmacy practice at Texas A&M Health Science Center Irma Lerma Rangel College of Pharmacy in Kingsville. "I don't recommend it," she says.

And there may be a drawback to some forms of zinc: In 2009, taking zinc nasal products was linked to a permanent loss of taste and smell in some people. The FDA has warned consumers not to use three zinc-based nasal products, but that warning doesn't extend to oral products, like zinc tablets or lozenges.

Echinacea
Studies on whether the herb echinacea reduces the duration of the common cold are a mixed bag. So much depends on the treatment's preparation—juice, root-and-herb or tincture—which can vary widely. One study found that echinacea pills were about as effective as placebo bills in shortening the length of a cold. What's more, echinacea is closely related to ragweed.

Allergic reactions to oral echinacea—like rashes and gastrointestinal problems—are uncommon. But if you have ragweed-triggered seasonal allergies, you may be more likely to experience side effects with echinacea.

Decongestants
Do they work? Yes. Over-the-counter decongestants relieve stuffy sinuses by shrinking the blood vessels that stop up the nose. Choose a product that contains pseudoephedrine (like Sudafed). You'll have to ask for it at the pharmacy counter—in 2005, the FDA put limits on how much an individual can purchase because pseudoephedrine is commonly used to make methamphetamine. That said, the drug is safe for most people and among the most effective cold remedies available.

"The quick rule of thumb is if you can buy it without showing an ID, don't bother. It's not going to work," says Ally Dering-Anderson, clinical assistant professor of pharmacy practice at the University of Nebraska Medical Center. Those with high blood pressure should stick to spray-based decongestants such as Afrin 12 Hour. This won't stray into your bloodstream, says Alonzo.

Vitamin C
Vitamin C in mega-doses comes brightly packaged as Emergen-C and Airborne, but there's no concrete evidence that large doses of C can reduce the duration or severity of colds or the flu. Vitamin C is water soluble, so anything over the recommended dietary allowance—which is 90 milligrams a day for men and 75 for women—will be eliminated from the body when you urinate. The better approach: Fill up on whole foods loaded with vitamin C, which are also loaded with other important nutrients to keep your body strong and healthy.

Expectorants
Expectorants such as Mucinex thin the nasty mucous draining down the back of your throat, which helps you cough it up and out. These products can help, but the best expectorant may be as near as your kitchen sink.

"All you need to do is drink more water," say Dering-Anderson. If you find water too bland for your tastes, try lemonade, tea, or even coffee, she says. You can also turn on the hot water in the shower and breathe it in or try a cool-mist humidifier.

Defend
This homeopathic remedy claims to fight multiple symptoms of a cold including "hacking cough" or "rattling/tickling cough." According to Alonzo, there's no data that show either way whether Defend works. In fact, the National Institutes of Health says that there's little to no evidence that any homeopathic products work. Homeopathic products are not as tightly regulated as drugs.

Antihistamines
Do they work? Yes. If your symptoms include runny nose and scratchy throat, an antihistamine may provide temporary relief. Often used to treat allergies, common brand names include Claritin, Zyrtec, and Benadryl. Claritin and Zyrtec aren't likely to make you drowsy. Benadryl will, but that can be a good thing when you need to get some rest, says Dering-Anderson.

Sambucol
Does it work? Maybe. Another homeopathic remedy, Sambucol consists of extracts from the black elderberry plant. One 2004 study reported that the extract cut flu symptoms down by four days. But the study was small, involving only 60 people; the researchers relied on participants' own reports of how they were feeling; and it was funded by the manufacturer of the product.

Pain relievers
A pain reliever may be the first thing you reach for when you come down with a cold, and with good reason. "Pain relievers for coughs and cold can be very effective," says Alonzo. They can also help with fever.

Anti-inflammatory meds like Advil or Motrin (ibuprofen) or Aleve (naproxen) have the advantage of reducing tissue inflammation, but you should take Tylenol (acetaminophen) instead if you're taking blood thinners to prevent blood clots or if you have stomach problems, congestive heart failure, or asthma and nasal polyps.

Theraflu
Theraflu is basically a dose of acetaminophen along with several other anti-cold ingredients and has a warning about the risk of liver damage if you take more than the recommended dose or mix with alcohol or other acetaminophen-containing products. Better bet: Take ibuprofen or acetaminophen alone and brew yourself a cup of tea or soup, says Dering-Anderson. You'll get the warm, soothing fluids without the extra drugs.