Nasal mucus, or snot, is a normal substance produced in the respiratory system. It serves as a protective barrier, lining nasal passages and airways. Mucus traps inhaled particles like dust, allergens, bacteria, and viruses, preventing them from reaching the lungs. It also moisturizes and warms inhaled air, keeping respiratory tract tissues hydrated.
How Snot Changes Color
Yellow snot indicates an active immune response. When an infection or irritant is present, the body sends white blood cells, specifically neutrophils, to the area. These cells contain myeloperoxidase, an iron-rich enzyme. As neutrophils fight pathogens, they release this enzyme, whose green pigment contributes to the yellowish or greenish hue of the mucus. The color change signals your immune system is working to clear the infection or irritant.
Common Reasons for Yellow Snot
Yellow snot often signals an infection, with viral infections like the common cold being a primary cause. When a cold virus infects nasal passages, the immune system sends white blood cells to the area. These cells release enzymes that turn mucus yellow as they neutralize the virus.
While often associated with viral infections, yellow snot can also occur with bacterial infections like sinusitis. The immune response intensifies, leading to a greater concentration of white blood cells and their enzymes in the mucus. This increased immune activity can result in a more pronounced yellow or greenish coloration. The presence of yellow snot alone does not definitively distinguish between viral and bacterial infections, as both can trigger a similar immune reaction.
When to Seek Medical Care
While yellow snot often resolves on its own, certain accompanying symptoms warrant medical attention. If yellow snot persists for more than 10 to 14 days, or if symptoms worsen after initial improvement, it could indicate a bacterial infection requiring treatment. High fever, severe facial pain or pressure (especially around the eyes or forehead) are also signs to consult a healthcare provider.
Other concerning symptoms include shortness of breath, vision changes, or a stiff neck alongside yellow mucus. These may point to more serious conditions needing prompt diagnosis and intervention. If an individual experiences recurrent episodes of yellow snot with other symptoms, a medical evaluation can help identify underlying issues or chronic conditions.