Blue phlegm is rather rare and it is usually colored due to a blue colored tablet or syrup that the person has consumed. Sometimes the pigment blue can come from one’s mascara as they move back into the tear ducts and join the nasal passage although this too is a rare phenomenon. There have also been patients who may not have eaten anything blue and yet the phlegm attains a bluish tinge. If the phlegm is bluish black in color, it could be due to smoking and in particular smoking up marijuana, cocaine and other similar substances. A person who has quit may continue to bring up this dark phlegm for weeks after she or he has quit. Other causes for this dark tinged phlegm are excessive air pollution, fungal infections of the lung, black lung disease that has affected thousands of coal workers over the years and serious medical conditions like cancer, tuberculosis and pulmonary disorders. If the bluish black liquid is being vomited out, it could very well be a sign of a stomach bleed and this will require immediate medical attention. It would be advisable to consult one’s local health care provider in case of differently colored phlegm to rule out chances of any serious illness.
On the home front it could be treated as one would treat the normal greenish yellow phlegm. Add a little roughly crushed white pepper to a teaspoon of honey. Consume this thrice a day to relieve the blue phlegm. Boil a cup of water and add the juice of one lemon and a teaspoon of onion juice while it boils. Just before taking it off the stove, add a spoon of honey to it and stir well. Allow the concoction to cool and drink it up in one go. Repeat this thrice a day for five days to clear up the phlegm. Inhaling steam can clear up the sticky phlegm by liquefying it and thus making its passage out of the body easier. Take a handful of fresh eucalyptus and fresh mint leaves and boil it in water. Take it off the stove and cover your head with a piece of cloth to inhale the steam and make sure that cloth covers the mouth of the pot as well. This will prevent the steam from escaping. Slice a lemon and on one half, spread a little black pepper and salt. Suck on it to ease up the phlegm.