Clear snot is in the normal range, while white mucus can mean you're congested and yellow or green mucus can sometimes mean that you have an infection.
Changes in mucus color, from clear to white to yellow to green, are part of the normal course of an illness. It's a sign that your immune system is fighting to get better. Pink, red, orange, or brown snot, on the other hand, is typically not from an illness.
Yellow phlegm is a sign that your body is fighting off a mild infection. "White blood cells are responsible for fighting infections, and as they get picked up in the mucus, they can cause it to have a yellowish hue," says Dr. Kreel.
During a common cold, nasal mucus may start out watery and clear, then become progressively thicker and more opaque, taking on a yellow or green tinge. This coloration is likely due to an increase in the number of certain immune system cells, or an increase in the enzymes these cells produce.
Green or Yellow Mucus
White blood cells rush to battle infection, and when they've done their job, they get flushed out of the body along with the virus. The yellow color comes from dead white blood cells, which can turn green if there are a lot of white blood cells and other debris.
Days 3 to 5: Cough and More Nasal Congestion
Nasal symptoms continue to develop, peaking during the third and fourth days. You may notice that mucus from your runny nose has become thicker, with a yellow or green tinge.
Even if you're coughing up yellow or green phlegm, you might not need antibiotics. Your mucus color alone can't tell you if a virus or bacteria is causing your cough. If your cough lasts longer than 3 weeks, it's time to see a healthcare provider. You may need an X-ray or antibiotics.
Signs and symptoms of a chest infection
coughing up yellow or green phlegm (thick mucus), or coughing up blood.
Small amounts of white mucus may be coughed up if the bronchitis is viral. If the color of the mucus changes to green or yellow, it may be a sign that a bacterial infection has also set in. The cough is usually the last symptom to clear up and may last for weeks.
Green and cloudy: viral or bacterial infection
A lot of the symptoms of viral infections – fever, cough, headache, loss of smell – overlap for COVID-19 and other viral infections like the flu, respiratory syncytial virus and the common cold. That's why COVID-19 testing and seeing a doctor is so important.
Coughing up phlegm is good if you are sick with the flu or another respiratory illness as doing so helps clear mucus from your lungs and prevents infection.
Does coughing up mucus mean you're getting better? In most cases, coughing up mucus means your body is working to fight off an infection, and it is in the healing stages. Drink plenty of fluids to help thin the mucus.
“Normally, mucus is clear. When you have a cold or infection, it might turn green or yellow,” said Alyssa. Clear snot usually signals allergies or some kind of environmental factor that is triggering your nose to start running, such as inhaling dust or allergens. Clear snot is nothing to worry about.
With pneumonia, you may cough up greenish or yellow phlegm. You also may run a fever and have the chills. Pneumonia can make it hard to breathe. You may feel like you've run up a flight of stairs when you were just sitting still.
An infection can make mucus thicker and stickier. Infections also lead to inflammation in the mucous membranes that line the nose and the rest of your airway. This can cause certain airway glands to make more mucus. That mucus can get thick with bacteria and cells that arrive to fight the infection.
Common symptoms of pneumonia include: a cough – which may be dry, or produce thick yellow, green, brown or blood-stained mucus (phlegm)
So, to answer your questions: The phlegm itself isn't toxic or harmful to swallow. Once swallowed, it's digested and absorbed. It isn't recycled intact; your body makes more in the lungs, nose and sinuses. It doesn't prolong your illness or lead to infection or complications in other parts of your body.
In general, your phlegm will last just about as long as your cough does. For bacterial infections, you can expect to see your cough and phlegm dissipate in 10 to 14 days, even without antibiotic medications. Viral infections can last a bit longer and may keep producing phlegm for up to three weeks.
In addition to lab tests, sputum or mucus from a cough can be visually examined to determine whether bronchitis is viral, bacterial, or both. Clear or white mucus often indicates a viral infection, while yellow or green mucus may suggest a bacterial infection.
Often viral cases of pneumonia begin as congestion and cough with or without fever in the first few days. When a doctor listens to the lungs and finds breathing sounds are not clear on either side of the chest, a viral cause over bacterial is even more highly suspected.
We're often told – even by doctors – that green or yellow secretions indicate you're infectious. But this isn't true. It's unclear how this myth arose, but it's likely a misunderstanding of the appearance and colour of pus.
About bronchitis
Bronchitis is an infection of the main airways of the lungs (bronchi), causing them to become irritated and inflamed. The main symptom is a cough, which may bring up yellow-grey mucus (phlegm). Bronchitis may also cause a sore throat and wheezing.
If a person with asthma produces yellow phlegm, it may be a sign that an infection or other condition is present. Common conditions that cause phlegm to turn yellow include pneumonia, bronchitis, and sinusitis. A person should contact their doctor if they have been producing yellow phlegm for more than a few days.