Studies confirm what teachers have long suspected: schoolchildren do get more colds than anybody else, suffering up to 10 a year, mostly in winter. Thirty children in a class, 10 colds each a year - that’s 300 separate cold infections! No wonder coughs, sniffs and snotty noses are fixtures of school life.

Luckily, as their teacher, you will not succumb to all of them. Children catch lots of colds because at school they are exposed to a range of viruses to which they have not yet become immune, and which they pass to one another.

Adults have built up immunity to many of these viruses, so on average fall victim to two or three colds a year. But teachers, who spend all their working hours in these viral breeding grounds, may catch more than their average share.

What we refer to as “a cold” is actually a set of symptoms triggered by any of up to 200 viruses. If a virus comes along that is identical to one you met last year, your immune system will be able to fight it off. But if a different one comes along, even though it causes the same symptoms, your immune system won’t recognise it, and your body will have to do battle all over again. This is why it is possible to get several colds one after another; and also why it has so far proved impossible to develop a vaccine.

A fortune awaits the first drug company to invent a cure for the common cold. At present, the only thing that can knock out a cold virus is your own immune system. You can make its job easier by resting, eating well, keeping war and drinking plenty of water. Antibiotics are ineffective because they only kill bacteria.

In spite of the common experience of colds following a chill or a drenching, experts maintain that colds cannot be “caught” from anything except contact with the virus, though we are more susceptible to infection when our systems are under stress - if overtired, for example.

Over-the-counter remedies, such as pain-killers and decongestants, can alleviate cold symptoms, as can old tried-and-tested remedies. Steam, for example, is an unfashionable way to clear a blocked nose: fill a bowl with boiling water (to which you can add a few drops of menthol, eucalyptus or Olbas oil), cover your head with a towel, and inhale the steam for 10 minutes or so.

Chicken soup, the “Jewish penicillin”, long touted as a cold cure, has been shown to contain a sulphur compound which causes the nose to run more freely, helping to eliminate infection.

On the other hand, there is no conclusive proof to support the claims made for vitamin C, which is taken by millions of people, or for zinc, said to reduce a cold’s duration and severity.

A widely used complementary cold-buster is the plant extract echinacea, which is said to work by boosting the immune system. This claim has never been proved, though studies have shown that the herb can relieve symptoms.

Since echinacea’s runaway success has come about mainly by people recommending it to each other, unprompted by high-profile publicity campaigns, it is tempting to think there must be something to it.