No 1 Wash your hands after being in a crowded place or in the same room as someone with a cold. This really works. A survey published in the American Journal of Preventive Medicine showed that episodes of colds and flu among 1,442 naval recruits at a training centre in Great Lakes Illinois almost halved after they were commanded to wash their hands more frequently.
The old theory about colds was that cold viruses were spread through the air, carried on tiny droplets of moisture that were then breathed in by other people. This is certainly one method of catching a cold, but experts now believe that many or even most colds are passed on via hands.
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No 2 Don't touch your nose and eyes unless you have to. We all do this many times a day without being aware of it. Once the virus is on your hands it's all too easy to transfer it and tears drain from the eyes via a duct into the nose so virus can easily spread from the eyes to the nose.
During a cough or sneeze, 40,000 infected droplets may be expelled as far as 30 feet. Some of these droplets will be deposited on objects, where the virus may survive for up to three hours, to be picked up by anyone who touches the object.
Door handles, handrails on public transport, light switches and crockery are common culprits. You can also pick up cold virus by shaking hands with someone who has recently blown their nose.
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No 3 We often pick up colds from people we have never met so wear gloves when you travel on public transport. Yes I know that to some people this might seem a bit over the top but it is very easy to pick up cold virus from handrails on the bus or Tube.
No 4 Your granny was right: you need to wrap up. In an experiment at Cardiff University's Common Cold Centre 90 volunteers spent 20 minutes with their feet in cold water and, surprise, surprise: 29 per cent developed cold symptom within five days compared to 9 per cent of the control group who simply dangled their feet in an empty bowl.
No 5 When wrapping up don't forget your nose - you should cover it with a scarf when the weather is cold. The importance of the effect of cold air in the nose is a new idea. Professor Ron Eccles, director of the Cardiff centre who came up with it, says that viruses multiply in the cells that line the nose, and they breed faster when the cells are cool.
No 6 Take a walk to boost your immune system: even on a cold day it still helps. Again it is to the USA that we have to turn for the relevant research.
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A study by Professor David Nieman at Appalachian State University in North Carolina examined the risks of catching a cold among a group of women aged between 65 and 84 over a 12-week period. Their findings revealed that walking for between 30 and 40 minutes five times a week almost halved the women's risk of catching a cold.
No 7 Fewer colds seems to be one advantage of getting older; most of us are able to fight off a good selection of the 200 or so different cold viruses without much difficulty.
After the age of 50, the average person has 1-2 colds each year, whereas 20-year-olds have 2-3 colds and small children have many more.
Over time, the immune systems of older people may have learnt to deal with a wide range of cold viruses. Also, many older people spend less time with children, who are the main reservoir of cold viruses.
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No 8 Try a nasal spray, such as Vicks First Defence (available from pharmacists). This jelly-like substance coats the virus so it cannot attach to the lining of the nose. It is also slightly acidic (which cold viruses dislike), and it stimulates secretions to wash the virus away. The idea makes sense, and preliminary research has shown it halves the likelihood of getting a cold.
No 9 Banish stress. It might be easier said than done, but it really seems to help. Researchers at the University of Pittsburgh asked 276 healthy volunteers about the stresses in their lives, and then deposited cold viruses in their noses. Those who had reported chronic stress (especially personal difficulties with friends or relatives) were more than twice as likely to become ill with a cold. It seems that chronic stress affects the immune system, and makes people less resistant to infection.
Learn more about how stress affects your health
No 10 Finally, don't waste money on Echinacea. In a study at the University of Virginia School of Medicine, USA, 473 volunteers were given either Echinacea or a dummy version for several days, and then a dose of common cold virus.
Sadly, the results, published in the New England Journal of Medicine in 2005, showed that Echinacea had no effect on the likelihood of developing a cold or its severity. Vitamin C does not fare much better.
Scientists at the Australian National Centre for Epidemiology and Population Health looked at 55 studies of vitamin C and the common cold, going back over 65 years and involving more than 11,000 people. They concluded that, for most people, taking vitamin C regularly does not reduce your chances of getting a cold. However it did have a noticeably good effect on marathon runners, skiers and soldiers exposed to extreme conditions.
Opinions about the efficacy of Echinacea vary among doctors and scientists. We take a look at the scientific evidence so far