Incredible facts about sputum

Chest examination of child with cough

We all know the misery of having a bad cough – and with the cough, we often cough up something nasty – known as sputum.

  • But what is sputum?
  • Where does sputum come from?
  • Is sputum important?

What is sputum?

Sputum is a mucousy substance, produced in the lower part of your airways.

Saliva is produced in the mouth. Snot is produced in the nose.

Of course when you cough, and produce a sample of sputum, it will also contain saliva and snot.

Where does sputum come from?

Sputum is made of mucous, produced from glands which line the airways. This provides a line of defence for the lungs from invading bacteria, viruses, and other foreign substances. It is a slippery, clear, water-based solution which contains enzymes, antibodies, and proteins. In essence, this means when you breathe in, the mucous is a kind of safety blanket, wrapping the lungs, and helping protect the airways from attack.

The airways are lined by tiny hairs called cilia, which beat in an upward motion, to bring mucus up out of the airways. Noxious chemicals in tobacco smoke paralyse these cilia, and this contributes to stagnant pools of mucous, increasing susceptibility to infection.

Normally our bodies produce 1–1.4L of mucous per day, but we are generally unaware of it.

Cough and sputum

A cough is a natural body reflex. You cough occasionally, if something tickles the back of your throat, such as dirt or dust. This is perfectly normal.

If however you develop a more persistent cough, you may be coughing up sputum. This is called a productive cough. Coughing up sputum may be a sign of lung disease.

What are the causes of a productive cough/sputum?

A cough can be short term – i.e. under 3 weeks duration, or chronic.

A cough lasting less than 3 weeks is self-limiting. If it lasts longer than this you should go and see your doctor.

Ventolin inhaler

Read more information on asthma and salbutamol inhalers from Dr Fox.

A chronic cough may be due to:

Does looking at your sputum help make a diagnosis?

Examination of your sputum can give a lot of information about your condition.

What is the colour and consistency of your sputum?

  1. Yellow/green – contains white cells and suggests infection such as pneumonia. Pneumonia may be caused by bacteria, or by viruses.
  2. Brown – may due to tar staining in smokers, or due to blood in the sputum, may be seen in people with occupational chest diseases such as coal mining and pneumoconiosis.
  3. Pink frothy sputum – can occur in heart failure.
  4. Blood in the sputum – a common presentation in lung cancer, and in patients with blood clots in the lungs – pulmonary emboli.

What happens if your sputum is cultured in the laboratory?

A sample of sputum can be cultured (grown)  in the laboratory to see if there are bacteria present. The lab can then do further tests to see which antibiotic the bacteria are sensitive to.

Why is sputum examined under the microscope?

A sputum sample can be examined under the microscope to look for lung cancer cells. This is called sputum cytology. Sputum can also be examined to look for evidence of tuberculosis (TB).

When should you see a doctor with a cough?

You should see a doctor if your cough:

  • Has lasted more than 3 weeks.
  • Is severe, or getting worse.
  • You are coughing up blood, have chest pain, or shortness of breath.
  • You have other symptoms such as unexplained weight loss, voice changes, or lumps in your neck.

Coughing up blood is a medical emergency.

  • Even if it is just a few streaks of blood – you must see your GP without delay.
  • Phone 999 if you are coughing up a lot of blood, or feel short of breath or have chest pain.

How to manage a cough

The first step to treating a cough is to find a diagnosis. Your doctor will ask questions and examine you. You may be asked to blow into a machine – called a Peak Flow Meter – to test your lung function. You may need a chest X-Ray, or an ECG.

Once you have a diagnosis, it is important to manage the underlying condition as well as possible.

Coughs due to viral infections

Most coughs are due to viral infections from infections in the upper airways. Most commonly these are respiratory syncytial viruses, or parainfluenza viruses for example. It’s very important to note that antibiotics do not have any effect on viral infections. The National Institute for Care and Excellence (NICE) have produced 2019 recommendations – based on up-to-date published medical research, about the treatment of cough.

They have stated clearly that with viral upper respiratory tract infections:

antibiotics make little difference to a persons’ symptoms.

Furthermore they have said –

Antibiotic resistance is a huge problem and we need to take action now to reduce antibiotic use. Taking antibiotics when you don’t need them puts you and your family at risk of developing infections which in turn cannot be easily treated.

These new guidelines will support GPs to reduce antibiotic prescriptions and we encourage patients to take their GPs advice about self-care.

How to self care with a cough

You can get help in assessing your cough by clicking on the NHS self-help guide: Cough.

  1. Stay well hydrated – this will help keep mucous thin and be easier to cough.
  2. Have hot, steamy showers as this helps to loosen mucous and clear sinuses.
  3. Avoid irritants such as perfumes, air fresheners, or cigarette smoke. There is so much help available, and now has never been a better time to give up smoking.
  4. Try a decongestant – these aim to reduce inflammation in your nasal passages and dry up nasal secretions. Examples include phenylephedrine and pseudoephedrine. These can be purchased as tablets, liquids  or nasal sprays. They can cause raised blood pressure, so should be used with caution if you have high blood pressure or heart disease.
  5. Try  a cough suppressant containing dextromethorphan – but only if you are coughing a lot at night.
  6. Try an expectorant. These work by which thinning out the mucus. Look for an expectorant  containing guaifenesin.
  7. Perlagonium is a herbal remedy for which there is some evidence of efficacy in treating the common cold. It has been shown to induce and support an immune response.
  8. Try honey! The NHS now recommends honey – and not antibiotics – for treating cough. In three published randomised clinical trials, children with respiratory infections given honey and lemon drinks, coughed less frequently at night.

Final thoughts

Most of us are unaware we have sputum – until something goes wrong. Living with a cough is most unpleasant. The vast majority of coughs are due to viral infections, usually in the upper airways and much can be done to treat these at home without the unnecessary use of antibiotics.

If you do cough, and this lasts for more than 3 weeks, do go and see your doctor. A correct diagnosis then means you can access the best treatment for your underlying condition.

For example, asthma is a common cause of cough and is often under-recognised. Your doctor can help make this diagnosis. This is an allergic condition which responds to the use of asthma inhalers. If you use your inhalers correctly, it is perfectly possible to control asthma symptoms and live a normal, healthy life.

Remember in September/October every year to ask your doctor about a flu jab!

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