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The lining of the respiratory tract is covered with mucous which is present from the nasal passages all the way down to the small air sacs in the lungs, called the alveoli. The function of mucous is to trap and protect the airways from bacteria, dirt and debris from entering the lungs.

Coughing up black coloured phlegm or sputum, or the presence of black streaks in phlegm, could be caused by several issues.

Dust or dirt

The most common cause of black coloured phlegm is dust or dirt from the environment. These particles are inhaled and then get stuck in the mentioned mucous when performing activities such as cleaning the house or working in the garden. 

Environmental pollutants

These products are also inhaled and get stuck in the protective mucous of the airways. This can result in sneezing and/or coughing and black sputum will then be produced. People who work in coal mines will experience this scenario.


Smoking cigarettes, marijuana or any other tobacco products can result in the production of brown, but also black sputum on occasion. The substances and chemicals which are found in the smoke of tobacco products cause damage to the lining of the airways which results in poorer mucous production and function.

Infections and chronic conditions

Certain types of fungal infections can affect the sinuses and the lung tissue. An infection such as mucormycosis, which occurs more commonly in diabetic patients, can cause an aggressive infection which results in damage to the soft tissue of the airways. Here, the mucous and phlegm can appear black. Chronic conditions such as lung cancer and emphysema can also produce dark coloured sputum.

Foreign bodies

Children, especially, like to put objects up their nostrils. These trapped objects can obstruct the production and flow of mucous which may result in bacterial infections. Parents will report a foul smell coming from the child's nasal passages and even mouth.

Management of black mucous production:

Stop using tobacco products

When patients stop using tobacco products, the mucous production actually increases and may seem darker. This happens because the cilia (which are hair like cells that sweep mucous out of the airways) 'wake up', since they aren't exposed to tobacco smoke anymore, and then move the debris out of the airways. The colour and amount of mucous being coughed up will decrease over a few weeks and these patients start feeling better as well.


Decreased fluid in the body results in thicker mucous being produced. Making sure that a person remains well hydrated, by drinking plenty of water every day, helps to thin the mucous out which makes it easier to expel.

Wear a mouth mask

People who are exposed to pollutants, chemicals or work in the mining or health industry, especially where highly transmittable infections are involved, should always be wearing protective mouth masks to prevent inhalation of these particles. 


If these preventative and treatment suggestions don't work to clear up black mucous production or if the coloured mucous remains persistent, then patients should consult their doctors in order to be assessed and managed further.

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