As a new 'super flu' strain sweeps the UK, with hospitalisations reaching record levels for this time of year, experts are urging Britons to pay attention to the colour of their snot as a key indicator of illness severity. The H3N2 subclade K variant is causing a surge in mucus production, and changes in snot colour can signal different stages of infection or underlying conditions.
According to the NHS, the body produces around 1.7 litres of mucus daily, which acts as a first line of defence by trapping viruses and bacteria. Clear snot is normal and often a good sign, though a very runny nose may indicate an allergy or, in rare cases, nasal polyps. Yellow snot suggests the body is fighting an infection, as white blood cells are flushed out with mucus. Green snot indicates the infection has taken hold, with the immune system in overdrive, and may warrant a visit to a doctor or pharmacist.
White snot often accompanies a cold or nasal infection, with inflammation slowing mucus flow and making it thicker. While usually harmless, asthmatics producing large amounts of white phlegm should ensure they take their preventer inhaler as prescribed. Red or brown snot typically indicates dried blood, often from a nosebleed or minor irritation, but coughing up large amounts of blood requires urgent medical attention.
Black snot is most common in smokers or those in polluted areas, but in rare cases can signal a serious fungal sinus infection, particularly in immunocompromised individuals. Pharmacist Abbas Kanani from Chemist Click advised that cold or flu symptoms usually clear within seven to ten days, but if mucus is coloured, persistent, and not improving after a few days, it is worth seeing a GP. He also recommended seeking advice if symptoms are accompanied by fever, chest pain, breathing difficulties, night chills, or unexplained weight loss.
