- Viruses may irritate airways, causing people to cough and spread their germs
- Mucus could stimulate cells in the respiratory tract to prevent it entering lungs
- Immune systems may release chemicals that damage airways and cause coughs
- Although unclear what the exact cause is, most coughs ease within a few weeks
- Researchers from The Hull York Medical School analysed past cough studies
It is the time of year where coughs and colds are rife. Now, a recent study published in the BMJ raises the question of why we wheeze when under the weather.
Although scientists from The Hull York Medical School, who carried out the research, are unsure of the exact cause, one theory is viruses have evolved to irritate infected people’s airways, causing them to cough and infect others.
People typically suffer two or three colds a year, with coughing being a common symptom.
Although irritating, most cases are not serious and resolve in a few weeks without treatment.
Here we look at the three different theories behind why we cough.
Scientists uncover the theories behind what causes niggling coughs this time of year (stock)
How the research was carried out
The researchers analysed past studies investigating cough.
Such trials typically assess guinea pigs or human airway cells as symptoms vary substantially from person-to-person.
The findings were published in the journal BMJ Open Respiratory Research.
Why do we cough?
One theory is the viruses that cause colds and flu have evolved to stimulate nerve receptors in our airways, causing irritation.
This sends a signal to the brain that causes infected people to cough up germs, which spreads the virus to others.
In such instances, coughing has no advantage for the infected person.
Study author Professor Alyn Morice said: ‘The most common form of cough is caused by upper respiratory tract infections and has no benefit to the host.’
Mucus is also known to stimulate nerve endings, which benefits the sufferer by allowing them to cough up the substance rather than it entering their lungs and causing further complications.
Others argue people’s immune systems release chemicals to fight infection when they are battling a cold or flu.
Such chemicals cause inflammation of the airways, which causes damage to its cell lining and stimulates coughing.