The winter season is rife for nose-blowing, with colds and flu spreading around like wildfire.

But what happens when you notice something coming out of your nose that isn’t supposed to be there?

Along with the usual green, yellowish or pale-colored mucus, you might spot flecks of black.

This is no doubt concerning – but doctors say it shouldn’t be.

There are several possible explanations for the black boogers – and most are nothing to worry about.

The color of your snot can give you a few hints as to why you have a runny nose. In some cases, for instance when it is clear, it is relatively harmless and usually caused by pollen allergies. If it is black, though, it could signal that you have been infected by a deadly fungus

Although rarely, it can be a sign of conditions like pneumonia, heart problems or even tuberculosis.

Perhaps the most surprising cause – yet one of the most common – is black eye makeup.

Dr Stuart Fischer, a family physician based in New York City, told DailyMail.com that make-up applied to the eyes can enter the tear duct and travel to the nasal passages. 

‘It makes sense that the mucus would then turn a different color.

‘But it isn’t likely to be jet black – secretions in the nose dilute it.’

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On TikTok, users post clips of their noses running with black liquid – and ask their followers if thick eyeliner could be to blame. 

One user replied to a clip posted by twiggy2.0 saying: ‘This happened to me a few times, don’t worry about it! It’s your sinuses connecting. The eyeliner most likely leaked from your waterline.’  

Other common causes, according to former nurse and medical writer Rachael Zimlich, include being exposed to high levels of pollution and black mold spores – such as on damp walls.

‘People in highly polluted areas breathe in particles that can collect in the lung tissue and appear in mucus,’ Zimlich wrote for Very Well Health. 

The same can happen if you’re near a large fire due to the smoke particles.

Those with weakened immune systems and underlying lung conditions are more at risk of developing infections caused by black spores, which cause the black mucus. 

A more obvious cause is smoking – as is lung damage caused by chronic use of cocaine. 

When it comes to less common causes, an unusual type of pneumonia found most commonly in coal miners can be to blame – dust enters the tissues of the lungs. 

Over time, deposits collect to form scar tissue which travels to the mucus membranes and is expelled.

In very rare cases, the bacterial infection tuberculosis is to blame – sufferers find they also cough up blood and experience chest pain.

A particular, rare type of lung cancer called bronchopulmonary melanoma creates masses, destroys healthy tissue and is known for producing dark, black mucus.