Is Green Snot Really a Sign of a Sinus Infection?

A sinus infection can cause green snot — but so can many other infections and irritants.

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You woke up feeling a bit off: a scratchy throat, congested nose, foggy head, the usual. When the first sneeze hits, you drain your nose into a tissue … and then peek at the slimy results. You see green.

“It must be a sinus infection,” you think, confidently. Your mom always said that green snot is a sign of a sinus infection. So was she right?

Kind of. Your snot color can change based on infections and irritants in the nose—but a sinus infection isn’t the only reason your snot can turn lime-hued.

Here’s how snot works: Your nose, sinuses, and mouth have mucus to hydrate the tissue lining, which prevents them from becoming too dry. The sticky mucus traps dust and bacteria to keep them from entering the rest of the body.

Your trusty mucus is always there, but you tend to notice it more when you’re congested and your airways are blocked. That’s because the body releases histamine after exposure to an infection, which increases blood flow to the nose and causes inflammation around the nasal tissues. As the nasal membranes become congested with blood, they produce excess mucus, according to the American Academy of Otolaryngology. (Try these home remedies for better breathing with a cold.)

So why the change in snot color? Blame enzymes. Your mucus contains white blood cells that prepare for battle when irritants (like pollen if you have seasonal allergies) or infectious bacteria or viruses enter the nose. To fight off the invader, the white blood cells produce enzymes, which contain iron. That iron gives mucus its dark yellow-green color.

Mom was onto something: If you have green snot, it could mean that you have a sinus infection. But your body may also just be reacting to an allergen or irritating pollutant, according to the Centers for Disease Control and Prevention (CDC). Your immune system can produce those enzymes that turn your snot green at any time, not just when you’re sick with a sinus infection.

Bottom line: Don’t immediately head to your doctor for antibiotics just because your snot is green. If you have a sinus infection, you may notice other key symptoms, like stuffy nose, headache, loss of smell, pressure and pain in the face, postnasal drip, sore throat, and bad breath. An acute sinus infection can often fade out on its own over a few weeks. Nasal saline rinsers, rest, hydration, and OTC pain relievers can make the recovery time a little easier. It’s a good idea to see a doctor for your sinus infection if symptoms get worse, last more than 10 days, or if you have a temperature higher than 100.4°F.

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