Pneumonia is inflammation of the tissues in one or both of your lungs. It's usually caused by an infection.
At the end of the airways in your lungs there are clusters of tiny air sacs called alveoli. If you have pneumonia, these tiny sacs become inflamed and fill up with fluid.
As well as making you cough, the inflammation makes it harder for you to breathe. It also means your body is less able to absorb oxygen.
Pneumonia symptoms vary - people can have different combinations of symptoms.
Symptoms can develop suddenly, for example, over 24-48 hours. However, they can also come on more slowly, over several days.
If you have pneumonia, you are likely to have difficulty breathing (dyspnoea). Your breathing may be rapid and shallow. And you may feel breathless, even when you are resting.
Other common symptoms can include:
- coughing up phlegm (thick mucus) that may be yellow, green, brownish or blood-stained,
- a rapid heartbeat,
- a fever,
- feeling generally unwell,
- sweating and shivering,
- loss of appetite, and
- pain in your chest.
Elderly people with pneumonia can show fewer symptoms. For example, they are less likely to have a fever than younger people.
Less commonly, symptoms of pneumonia can include:
- coughing up blood (haemoptysis),
- vomiting, and
- pain in your joints and muscles.
More severe symptoms can include:
- your skin turning ashen or blue (cyanosis), and
- feeling confused and disorientated - particularly in elderly people.
Pneumonia symptoms can be similar to those of other chest infections, such as acute bronchitis.