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Airways and respiratory system

An adult breathes about 15,000 litres of air in and out every day: about enough air to fill a middle-sized room. For the airways - which go from the nose to deep in the lungs - this means a constant inflow of dust, toxins and germs. Healthy airways have a variety of self-defence mechanisms. But no defence system is perfect. Viruses and bacteria can still get in. When the system is too sensitive and over-defensive, people can develop problems like allergies and asthma.

Feature: The common cold

What is the common cold? How is it different from the flu? The cold is an infection that is usually caused by viruses and develops over a few days. It usually starts with a scratchy or sore throat.

Research summaries

Echinacea

It is not clear whether echinacea extracts can prevent colds. Taking some echinacea products when a cold starts might help to reduce the cold's length and severity. Because the available products are very different to one another, more research is needed to be sure. Adverse effects are rare. more...

Asthma: Does breathing training help?

Training in breathing techniques could help people relax. Whether it can also relieve asthma is still not clear. more...

Common colds: Can antibiotics help?

The adverse effects of antibiotics probably outweigh the benefits of antibiotics for uncomplicated colds. They might be worthwhile only when a cold does not get better as fast as usual or there is bacterial infection. more...

Common colds: Can vitamin C prevent or relieve them?

Taking vitamin C every day does not prevent colds. However if you have a cold, it might be able to shorten the cold by about a day. more...

Common colds: What happens if you wait before trying start antibiotics?

Antibiotics are not going to help most children with simple colds, and will only help with middle ear infections a bit. This needs to be balanced against the adverse effects, and waiting a day to start the antibiotics might mean they are no longer needed. more...

Common colds: Should we follow the "drink more fluids" advice?

There is no medical reason to drink more than you feel like drinking when you have a cold. more...

Sore throats: Do antibiotics help?

Antibiotics can shorten sore throats caused by infections by less than day. There are adverse effects, though, so that weighing up the pros and cons is an individual exercise. more...