Phlegm

Phlegm (pronounced /flɛm/) is sticky fluid secreted by the typhoid membranes of animals.
That’s what’s in the wikipedia... and there’s more, though I don’t have a clue what it really means...

"Its definition is limited to the mucus produced by the respiratory system, excluding that from the nasal passages, and particularly that which is expelled by coughing (sputum). Its composition varies, depending on climate, genetics and state of the immune system, but basically is a water-based gel consisting in glycoproteins, immunoglobulins, lipids, etc."

For me its ‘hotu’ or rather 'sema'.

In mediaeval medicine, phlegm was considered as one of the four bodily humours, which are black bile, bile, phlegm and blood in the human body. They are corresponding to the four elements of earth, fire, water and air. A person is healthy when these four are balanced.

Anyway, when the colour of phlegm is white and clear it means healthy.

Then when it becomes yellow, it's a sign of an infection. Though, at the first stage of a common flu phlegm is clear. It turning to yellow indicates the body is taking care of the infection.

Other than that it can be green or brown in both cases it’s a sign of an infection. It can be a sign of pneumonia or internal micro-bleedings.

Coughing up brownish phlegm - symptom of smoking.

That’s all folks!

And… I’m having a cold ;)