When we are ill, especially if it is an illness that involves a hacking cough, it is not uncommon to cough up phlegm, or sputum. While you may mostly think nothing of it, simply associating it with your current illness, the color of this mucus can tell you a lot about the pathogens that have invaded your body.
The body is a mucus-making machine, producing around 1 to 1.5 liters of this gel-like substance every single day, even when you're healthy. Dr. Matthew Exline, a pulmonologist and critical care specialist at The Ohio State University Wexner Medical Center, explains that, "In health, phlegm/mucus is mostly clear and minimal. If you are coughing up significant amounts of phlegm you could have an infection or allergies.
While coughing up some clear phlegm is normal, larger amounts of phlegm may indicate and underlying infection. This occurs because the respiratory tract has become inflamed, which leads to the coughing. In turn, this coughing speeds up the rate of infection.
So, since we've gotten clear phlegm out of the way, let's take a look at what other colors of phlegm mean for our health.
White or Gray Phlegm
If you're coughing up white or gray phlegm then this could be a sign of an upper respiratory tract infection or sinus congestion. Dr. Steve Okhravi, an emergency physician and founder of DocChat and emergency Medical care, states that this kind of phlegm drains from the sinuses - "Normally, your sinus doesn't drip, but when there's inflammation, either viral or bacterial, it can cause a drip from your sinus into your throat."
You might have heard that dairy products can cause this type of mucus to develop, but this simply isn't true. However, dairy can make it thicker, making it harder for the body to drain. This causes the mucus to dry out, leading to a white discharge. Meanwhile, coughing up gray phlegm could be a sign that your body is trying to rid itself of resin or tars that have accumulated as a result of excessive smoking or inhalation of air pollutants like smog or dust.
Green or Dark Yellow Phlegm
Coughing up thick and dark yellow phlegm could be a sign of a viral or bacterial infections, or a lower respiratory tract infection. Usually, this occurs when they body's immune system sends white blood cells, known as neutrophils, to the area of infection. These cells contain a green protein, which, when present in large numbers, give the mucus a greenish tint.
However, a study published in 2011 in the European Respiratory Journal found that green or yellow phlegm is not always an indication of an infection. After some tests were carried out, researchers found that only 59% of every 100 sample of green phlegm contained bacteria while only 46% out of every 100 samples of yellow phlegm contained bacteria. Therefore, having green mucus does not necessarily mean you have a bacterial infection.
Smokers tend to produce more brown phlegm, which often comes out mixed with saliva in a grainy texture. Smoking can cause your phlegm to turn brown because of the resin, tar and other particulate matter in cigarettes, which the body is trying to expel.
If you don't smoke and are coughing up brown phlegm, it could be down to the food and drink that you're consuming - Chocolate, coffee, and red wine to name but a few.
Coughing up pink phlegm could be a sign of a pulmonary edema, also known as fluid on the lungs. When seen in small amounts, it can also be a sign of bleeding. This type of phlegm can sometimes have a frothy texture - this is especially common in those who have pre-existing heart problems.
Blood in the phlegm is known as haemoptysis, while streaks of blood in phlegm is a benign sign of bronchitis. Coughing up a large quantity of bloody phlegm could be a sign of tuberculosis, pneumonia, cancer, or pulmonary embolism. If there is excessive bleeding, more blood than phlegm, or no sign of it stopping, you should seek medical advice immediately because you could be dealing with a very serious health problem.