If you are among the thousands of British people to have called in sick from work this week with a cold (you probably called it flu - it sounds so much more convincing that way, doesn't it?), you may have tried a range of remedies, bought or home-made. Chances are none of them will have cured you. You may be kicking yourself for not wrapping up warmly enough. Or, more likely still, you are kicking someone you know for infecting you. There, too, you could be mistaken. We all think we understand the common cold. Yet few of us have a clue about how we get it or what to do to shake it off.

Take snogging. You would have thought that French kissing a snotty lover was a bad idea on many levels. But contrary to widespread belief, it is very hard to catch a cold by exchanging saliva. In 1984, researchers had the unenviable job of observing hundreds of students snogging. Kissing, they concluded, resulted in no transmission of the cold virus. "The virus travels in the mucus from the respiratory system," explains Professor Ron Eccles, director of the Common Cold Centre at Cardiff University. "Unless you have a bad cough, and some of the respiratory mucus has made its way into your saliva, the cold virus will not be transmitted by kissing."

Most of us think colds are highly contagious. Certainly, most adults get two to five colds a year (schoolchildren can catch double this number). But scientists say colds are not, in fact, terribly easy to pass on. Under laboratory conditions, when healthy volunteers are kept with those suffering colds, it is remarkably difficult to spread the infection. This is because the mucus from the respiratory tract of someone infected has to get directly into your respiratory tract.

To do this, an infected person must either sneeeze or cough near you so you inhale their infected droplets, or touch a surface, allowing you pick the virus up on your fingers (a cold virus can live on a doorknob for hours). You then rub your eyes or touch your nose (your eye drains into your nose), depositing the virus in your own respiratory tract.

Since you touch surfaces handled by thousands of individuals every day (just think of the handrail on an escalator) and breathe in the droplets of a variety of sneezing strangers, it would be harsh to blame your loved ones for every sniffle you develop. Indeed, for every symptomatic individual, there are two or three infectious people touching things with virus-infected fingers. Handwashing may reduce infection rates, but, as Eccles admits, "You'd have to wear a space mask to rule it out entirely."

Since so much is known about cold viruses, it seems amazing that no pharmaceutical company has come up with the cure that would make its fortune. There are a couple of flu "antiviral" injections in use which, if administered within the first 24 to 48 hours of illness, are said to shorten some flu bouts by a day or so. But these will not touch a cold.

Cold viruses, while they manifest many "flu-like symptoms" (fever, runny nose, cough), are different from flu viruses. Cold symptoms come from 200 different viruses (though up to half of all colds are the fault of one culprit, the "rhinovirus"). To kill a cold you would have to kill the specific cold virus that has seized you. One American company did recently invent a vaccination against the rhinovirus but, says Eccles, "It had to be taken off the market because women taking it kept getting pregnant" - the injection apparently interfered with the contraceptive pill.

So do we just have to accept colds as inevitable? In recent years the myth that you catch a cold by getting chilly seemed to have been debunked. But now there is a backlash that grannies everywhere will welcome: "If you expose the skin to a cold stimulus, this constricts your blood vessels," says Eccles. "Since your immune system resides in your blood, this constriction can restrict the activity of your white blood cells" - thereby inhibiting your ability to fight off a cold virus.

Indeed, he says, it may be that we get more colds in winter not just because we are crowded into overheated spaces, but because our noses are cold (and are therefore more vulnerable to flying viruses).

Proactive types swear by Echinacea or vitamin C to avoid a cold. The clinical evidence on Echinacea is inconclusive (a 2003 study found no effect). Vitamin C, meanwhile, has no proven effect in preventing a cold, but, says Eccles, "it may reduce the severity and duration of one because it is an antioxidant". Antioxidants boost your immune system, and, as Eccles puts it, "Your immune system is the cure for the cold: in seven to 10 days, your immune system will overcome the virus." Coughing, though, can last 10 weeks. Similarly, other foods such as garlic - another clinical "grey area" - peppers and onions have "antiviral properties" that may help fight the virus (possibly explaining the clinically unsubstantiated adage, "feed a cold and starve a fever").

Indeed, "Any hot and tasty food or drink that promotes mucus is a good idea," says Eccles. "Mucus secretion in the airways is a beneficial symptom - it washes out the virus." Eccles recommends a good curry.

Over-the-counter cold treatments might not be a waste of money either. Lemsip is mucus-producing; for a cheaper route, drink hot honey and lemon and take paracetamol for your headache. Nasal congestion, caused by swelling of the large veins in the lining of the nose, often stops you sleeping, so decongestant sprays and other nighttime remedies can help you fight a cold, says Eccles, because they promote sleep, which restores your busy immune system.

Finally, help doesn't have to be hi-tech: a hot toddy, while it won't prevent a cold, is certainly medicinal. "One or two units of alcohol in a hot toddy can be a great sedative," says Eccles. Doctor's orders, then.