Green snot is a common symptom, often mistaken as an allergic reaction. However, it generally indicates the body actively fighting an infection. Understanding snot color can provide clues about respiratory health.
What Snot Color Indicates
Mucus protects the respiratory system by trapping dust, allergens, and microbes. Healthy mucus is clear, thin, and watery, containing proteins, antibodies, and salts. Its color and consistency change with irritants or infections. White mucus suggests congestion, indicating moisture loss and thickening.
Yellow or green snot indicates an active immune response. This color shift is due to white blood cells, especially neutrophils, which are important for fighting infections. These cells release myeloperoxidase, an iron-containing enzyme that gives mucus its greenish hue. The intensity of the green reflects the concentration of these immune cells and their byproducts.
Distinguishing Green Snot: Infections vs. Allergies
Green snot is commonly associated with viral or bacterial infections. When pathogens enter nasal passages, the immune system sends white blood cells to combat them. The green color signifies these immune cells are eliminating the infection, and their breakdown products are expelled. Viral infections, like the common cold, may start with clear or white mucus, turning yellow or green as the immune response escalates. Bacterial infections often cause thicker, persistently green or yellowish-green discharge, sometimes with facial pain or fever.
In contrast, snot from allergies (allergic rhinitis) is typically clear, thin, and watery. Allergy symptoms occur when the immune system overreacts to harmless triggers like pollen, dust mites, or pet dander. This reaction releases histamine, causing itchy eyes, sneezing, a runny nose, and sometimes a sore throat from postnasal drip. Unlike infections, allergies usually do not cause fever or body aches. Allergy symptoms are often immediate upon allergen exposure and persist as long as exposure continues, while cold symptoms develop gradually and typically resolve within 7 to 10 days.
When to Consult a Doctor
While green snot often indicates a normal immune response to an infection, certain accompanying symptoms warrant medical attention. Consult a doctor if green snot persists for longer than 10 to 14 days without improvement. Also consult a doctor if symptoms worsen after initial improvement, which could suggest a secondary bacterial infection.
Other concerning signs include a persistent high fever, severe headache, or facial pain and pressure, especially around the eyes, cheeks, and forehead. Difficulty breathing, chest pain, or blood in the snot require immediate medical attention. Individuals with compromised immune systems, infants, or those experiencing confusion or changes in vision should seek medical care.