Dr Tom Smith answers your health questions

Fears about bird flu

I've been told the NHS is stockpiling vaccines for bird flu. This worries me - I thought it was no longer such a concern. Are we still expecting it to strike in the near future?

Predicting flu epidemics is very imprecise. We have been expecting a pandemic since 1968, but it has never materialised. The World Health Organisation (WHO) has about 80 centres worldwide that monitor the emergence of all new flu viruses. They stockpile samples of all the viruses they think might be needed for manufacture of vaccines - many of which are never used. I suspect bird flu virus is in that stockpile, so it can be used for vaccine production if there is any sign that its ability to transfer into a human-to-human infection (at present virtually zero) is changing. As far as I can find out, no manufacturer is producing massive amounts of the vaccine for use in the near future. So keeping samples of bird flu virus is simply a sensible precaution, and is not related to fears of an impending pandemic.

I'm half awake when I'm asleep

I have a strange problem: I have no problem falling asleep, but throughout the night I am vaguely aware of being half-awake. When I wake, I feel exhausted. What can I do?

Do see your doctor about this. Something has disturbed your normal pattern of sleep, and it's hard to say what it is without a detailed investigation. Your doctor may refer you to a sleep clinic. Investigation of sleep disturbances is a complex science, and you may need expert advice, especially because you are sleepy in the mornings. That has its obvious dangers if you drive, say.

Is my new TV causing headaches

Last April I had a large flatscreen TV installed. Within weeks I started to develop sore eyes and extreme headaches. I have had three eye tests and was told I was not producing enough tears, so I am using drops - but the optometrists could find no reason for the headaches. I had a CT scan and this was clear. Any ideas?

What stands out is that you date the headaches from the new TV. Did you install it in the wall above your natural viewing position? In other words, do you look up at the screen? Tilting the chin upwards to view a screen is the perfect way to provoke a tension headache because you're tensing the neck muscles connecting the upper back to the back of the skull. It is always best to look down on a screen, so the chin is tilted slightly downwards. Shift the centre of the screen to below the level of your eyes.

Why do we have to blow our nose?

It's unsavoury, I know, but every time my six-year-old son gets a cold, he wants to know why we have snot and what it's made of - can you help me answer?

A pleasure. Snot is made up of three main ingredients. Its basis is mucus, which is produced by the cells lining the nasal passages as a physical barrier to, or trap for, germs and dust entering the nose as we breathe in. It is produced all the time, and is normally carried away and eventually absorbed or swallowed. When we have an infection, the mucosa (the layer of cells that produce mucus) becomes a battleground between the invading bacteria or viruses and our white cells and serum (containing antibodies) that we direct there to kill them off. Snot is our first line of protection and a sign that our antibacterial (or anti-pollen and dust) mechanisms are in place.

Thanks to guardian.co.uk who have provided this article. View the original here.