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Does this Look Green to You? What the Colours of Mucus Mean

Last year was a banner year in the Foster household: the months of September and October alone saw us through at least six different cold viruses between my two boys. I’m expecting a similar showing this year. After only one week back in preschool—as if on cue—my 4-year-old developed a runny nose.

And so it begins.

If you’re a mom, I know you’ve wiped a tiny red nose or two. And I’m almost positive you’ve glanced at the contents of that tissue. Have you ever wondered what it means?

As a family doctor, I hear this statement a lot from parents: “When the mucus turned green, I knew we had to bring her in. I knew she had an infection.”

Sound about right?

Well, I’m here to report that this commonly-held belief is, unfortunately, false. You may have heard that green nasal discharge is a definite sign of bacterial infection, but it’s not.

So what does green mucus mean?

When you have a cold, a certain type of white blood cells (neutrophils) flood to the area to fight the virus—these cells contain an enzyme that’s green in color, so if there are a lot of the cells, the mucus will appear green, too. There may also be a bacterial infection, or there may not be. The green colour alone is not a reliable indicator.

In fact, your kid can have perfectly clear mucus and also have a full-blown ear infection or horrendous flu infection.

(While we’re at it, if you’re feeling less than clear on the difference between a cold and the flu, read this.)

And What does red mucus mean?

Is it a sign of infection when mucus is tinged with brownish or reddish blood? Again, not necessarily. When a nose gets irritated from all that rubbing, blowing, and wiping, the lining just inside the nostril can bleed a little. It’s not a cause for alarm if you see a small amount of blood in nasal mucus, but if you see large amounts of blood, it’s a good idea to visit the doctor.

So if the colour of mucus isn’t terribly reliable, what is a more reliable indicator of a bacterial infection? Symptoms like: fever, lethargy, and a deterioration in symptoms instead of the improvement you would expect after a few days battling a virus—these are all good indicators that it's time to see your doctor.

Now, although mucus may not tell you much about what kind of infection your little one has, I can almost guarantee you're going to be dealing with a lot of it this fall and winter.

Here are some of my suggestions on how to manage cold and flu symptoms (this is what I recommend for patients and what I use at home with my own kids):