What is snot?
Snot is mucus produced in your nose. Membranes on the inside of your nose are lined with cells that make it. This mucus lining traps dust and germs that you breathe in.
Tiny hairs move the mucus down your nasal cavity to where you swallow. When you swallow, the mucus goes into your digestive system (gut).
You usually produce around 1-2 litres of mucus each day, but if your sinuses or other parts of your upper respiratory tract (upper airways) are inflamed, you can produce twice as much. Inflammation of your upper airways can be caused by dust, smoke, pollen, chemicals or infection.
If you have an infection, your body makes extra mucus to trap and get rid of the germs. The extra mucus that is not swallowed comes out your nose as snot.
What is sputum?
The same process occurs in your lower respiratory tract (lower airways), such as your trachea (windpipe), bronchi (airways into your lungs) and your lungs.
Mucus is produced in the surface tissue of these airways to keep it moist, which makes it easier for the air you breathe to get past. Cells move the mucus up towards your throat where you swallow it.
When you have an infection, your body makes extra mucus to trap and get rid of the germs. This triggers an increased urge to cough, and you cough up the mucus as sputum. Coughing also irritates your lower airways and leads to even more mucus production.
What does the colour of my snot or sputum mean?
The colour of the mucus tells you what’s going on in your airways. It tells you how inflamed your tissues are and shows you that your immune system is fighting off the infection. The yellow-green colour of snot means there are more neutrophils, white blood cells that fight infection.
Changes in colour are usually not a cause for alarm and doctors don’t usually use this as part of their diagnosis.
Use this interactive tool to work out what is happening with your snot: What the colour of your snot really means
Do I need antibiotics if my snot or sputum changes colour?
The colour of your snot or sputum doesn’t tell you whether your infection is bacterial or viral. Antibiotics only work against bacterial infections. Taking antibiotics when you don’t need them can cause antibiotic resistance and may make you sick.If you have a blocked or runny nose, you can try breathing in steam, use a nasal decongestant or try a salt water (saline) nasal spray or rinse to get some relief.
A cough can sometimes settle by breathing in steam, sucking a cough lozenge or by using an inhaler from your doctor. Read more about cough in adults and cough in children.
Read about the different respiratory tract infections to find out which one you have, whether you need to see a doctor and what you can do to take care of yourself at home.
- Acute sinusitis
- Chronic sinusitis
- Cough in adults
- Cough in children
- Respiratory tract infections
- Cold season – managing without antibiotics BPAC, NZ, 2018
Dr Sharon Leitch is a general practitioner and Senior Lecturer in the Department of General Practice and Rural Health at the University of Otago. Her area of research is patient safety in primary care and safe medicine use.