For centuries, people have been coming up with all manner of folk remedies for colds. Vitamin C supplements. Orange juice. Chicken soup. Tea with honey. Though everyone kind of acknowledges that these are far from scientific treatments, that leaves the question: What is the scientifically best way to avoid suffering a cold?

Soap. The answer is plain, regular soap.

Doctors from Canada and New Zealand looked back on 67 randomly controlled trials of various cold prevention and alleviation remedies, and found that above all else, clean hands are the most effective weapons against colds. This makes sense, considering our hands are what most commonly come in contact with potentially infected surfaces

Other steps to take? Zinc supplements, maybe.

“The best evidence for the prevention of the common cold supports hand-washing and possibly the use of zinc supplements,” said Dr Michael Allan, of the Department of Family Medicine, at the University of Alberta.

While at least two trials on children indicated that taking zinc had lower infection rates and school absences, there is little definitive evidence beyond that correlation. Natural remedies, like garlic, ginseng and other homeopathic treatments had no effect on cold prevention.

Already have a cold? Put down the vitamin C supplements. The best you can hope for from vitamin C is a reduced cold duration, and evidence for that is flimsy. Since about 95% of colds are caused by viruses, the best treatment is rest, a healthy diet and fluid intake. Pain relievers like ibuprofen can help with headaches and fevers, and decongestants with antihistamines will help with upper respiratory issues. Other than that, the body’s immune system works alone.

The common cold affects adults approximately 2-3 times a year and children under age 2 approximately 6 times a year, and can last anywhere from seven days to three weeks. There is no known cold vaccine, but for the most part the illness is more of a nuisance than it is debilitating.

Keep those hands clean.