DEAR DOCTOR K:
I’ve been under the weather for a few days. This morning I blew my nose and saw greenish mucus, so I called my doctor and requested antibiotics. He refused. Why?
Your doctor is correct not to prescribe antibiotics based on the color of your mucus alone. Despite what many people think, you cannot rely on the color or consistency of nasal discharge to distinguish viral from bacterial sinus infections. That’s an important distinction because only bacterial infections respond to antibiotics.
Color and consistency aren’t even good indicators of whether you’re dealing with an infection at all. Seasonal allergies, for example, can cause thick or thin, yellow, green or clear nasal discharge — even though there’s no infection at all.
Why do we have mucus in the first place? For one thing, it’s important for hydration. Mucus is found on tissues that come into contact with elements from the outside world, such as the lining of the nose, sinuses and mouth. These tissues would dry out and crack if mucus didn’t provide moisture.
Mucus is also important for protection. It is thick and sticky, so it can trap dust, bacteria or other unwanted passers-by in the air and prevent them from entering the body. Mucus also contains immune system cells, including white blood cells, which kill any bothersome trespassers it catches.
When the white blood cells in the tissue lining encounter an irritant or infectious organism, they produce enzymes to repel the invaders. These enzymes contain iron, which can give nasal discharge a greenish color. If the mucus remains in place (as when you’re sleeping), it becomes more concentrated and so may appear darker yellow or green. This is the natural order of things, whether the offending agent is a virus or a bacterium.
Most sinus infections are viral and will not improve with antibiotics. So it makes little sense to treat every episode of thick, green mucus with antibiotics.
That being said, there are times when antibiotics are warranted. For example, antibiotics might be worth considering when:
- an infection drags on for more than 10 days, or gets worse after a week;
- the discharge is thick and uniformly white (it looks like pus);
- there is a high fever that isn’t improving;
- severe symptoms do not respond to the usual over-the-counter sinus and cold remedies.
An overuse of antibiotics has caused an epidemic of antibiotic-resistant bacteria in our environment. Antibiotics can be very beneficial, even life-saving, when used appropriately. But when you’ve got a viral infection, they can’t do anything for you. All they can do is cause side effects and increase the risk of antibiotic-resistant bacteria.
The bacteria that cause the most common infections (like pneumonia, urinary tract infections and sexually transmitted diseases) have increasingly developed resistance to antibiotics. The World Health Organization, for instance, has warned that gonorrhea may soon become untreatable.
Your doctor is wise to be cautious in prescribing antibiotics. Too much of a good thing can be bad.