Your child has just gone back to school.

He may not be sniffling yet. But it is very likely that he will fall prey to several episodes of runny nose in the course of the school year. This is because schools are the hotbeds of cold viruses.

Dr Thomas Loh, chief and consultant of the Department of Otolaryngology at the National University Hospital (NUH), said the spread of colds in schools is prevalent.

'One of the reasons is the constant close contact between children. Sneezing and talking can spread droplets,' said Dr Loh.

'Another reason is that, unlike adults, children may not have immunity to different viruses.'

By and large, a runny nose is something that you can sneeze at: Common colds go away on their own and do not do much damage although the accompanying stuffy nose, fever, cough, general tiredness and muscle pain may be tiresome.

But just wait for it to take its course.

As Dr Chao Siew Shuen, a consultant from the Department of Otolaryngology at NUH, explained: 'It may help you feel better if you were to take over-the-counter medications, such as anti-pyretics and antihistamines, but the medicines do not help you to recover any faster.'

It is also important to know what causes your child's runny nose, as it could be something more serious than a common cold.

In that case, it might even require antibiotics, as in the case of bacterial rhinosinusitis.

The inflammation of the paranasal sinuses and the nasal cavity, said Dr Chao, causes symptoms which include mucus that contains pus, a blocked nose, facial pain or pressure, facial fullness and a cough or sore throat.

These symptoms may last for up to four weeks. Doctors usually diagnose bacterial rhinosinusitis if the symptoms last for 10 days or more, or if the child gets worse within 10 days after initial improvement.

Then there is the kind of runny nose which cannot be cured with any medicine: allergic rhinitis.

Said Dr Chao: 'Allergic rhinitis is a highly prevalent disease in developed countries. The prevalence of chronic rhinitis in Singapore is reported to be 44 per cent in children and 13-33 per cent in adults.'

When someone has allergic rhinitis, the nose runs because he has been exposed to certain substances. That means that if he does not know the actual cause and avoid the substance, he would not be addressing the root of the problem.'

Some of the symptoms of allergic rhinitis include a runny, stuffy or itchy nose, sneezing, itchy eyes or excessive tearing, asthma or eczema. Allergic Rhinitis may also run in the family.

In Singapore, according to Dr Chao, it is most common for house dust mites, cockroaches and animals to cause allergic rhinitis.

For those who have common colds caused by virus or bacteria, however, Dr Loh suggests that the child wear a mask and not share the same food or utensils or interact with the rest of the family until he or she has recovered. However, he conceded: 'This may not be practical.'

He added: 'In any case, it may not necessarily be all bad to catch a cold. Once we catch a cold, we should develop immunity and should not get any infection if we come across the same strain the next time.'