Most people get between two and five colds a year – hence the term "the common cold". Colds are caused by more than 200 different viruses, all of which result in the familiar runny nose, cough and sneezing. Colds can also give you earache, headaches, a sore throat, muscle aches and mild fever. It can be hard to know whether to stay in bed or struggle on and risk infecting colleagues. And since colds can cause sinusitis and ear infections, could you do more to prevent catching one?
The Common Cold Centre at the University of Cardiff, which carries out clinical trials on colds, is clear on prevention: you would have to be a hermit to avoid catching one. Colds are spread by virus particles expelled from the nose of someone in close contact. The virus travels on a bit of mucus from that person's nose and you inhale it. The cold virus also lurks on towels or door handles. If your fingers pick up particles and then touch your nose or eye, you can infect yourself.
Aside from being a hermit, you can reduce your infection rate by ensuring you – and your family – wash your hands regularly and properly (lathering both sides with soap for at least 20 seconds). Children are most likely to infect you, so wash your hands after wiping their noses. Colds are most infectious for the first two days.
It is not clear if being cold increases your risk of catching one. A study at the Common Cold Centre on two groups of 90 students found that those who had their feet chilled by sticking them in cold water for 20 minutes had twice as many colds as those who didn't. The researchers say that being chilled may have brought out the symptoms rather than actually increasing the students' rate of catching a cold virus. But you could argue that there's no harm in keeping your feet dry and warm.
There is no evidence that vitamin C prevents colds, even at high doses, according to a systematic review from the Cochrane Collaboration, which adds up all available evidence. If taken regularly at 1g a day it may reduce the length of colds by 8% in adults and 13% in children. You should not take high doses without checking with your doctor first, as it can cause problems in people with diabetes and some other conditions.
Zinc supplements taken for more than five months may protect against colds, according to another Cochrane review, but they can give you a funny taste in the mouth and upset your stomach and they aren't cheap so may not be worth the effort.
Some people swear by echinacea, but there is no evidence (again, according to a Cochrane review) that it prevents colds. In August, the Medicines and Healthcare Regulatory Agency said the herb shouldn't be given to children under 12 because of a risk of allergic reactions.
And if you can't prevent a cold, remember that antibiotics can't cure it.