Green or yellow snot doesn't always need antibiotics
Snot is the mucus that comes from the nose. When your immune system is fighting a cold virus, one of the first symptoms is a clear runny mucus from the nose. As the cold develops, the mucus can become thicker and yellow, and then green. Infection-fighting blood cells cause the change in colour and texture as they flood to the nasal area and increase in number as the cold progresses.
Infection-fighting white blood cells
Yellow snot indicates that the cold is progressing and when it turns green your immune system is really battling the infection. Some infection-fighting white blood cells contain a green substance (a protein) so the more these cells are present, the greener your snot will be.
No need for antibiotics
Green snot, or phlegm if you have a cough, is not necessarily a sign of a bacterial infection that will need treatment with antibiotics, according to Public Health England and the Royal College of General Practitioners (RCGP). In most healthy people production of yellow or green snot, with or without a cough, will stop when the cold or 'flu-like illness' clears up.
Public Health England says it is a prevailing myth that anyone with green phlegm or snot needs a course of antibiotics to get better. Most of the infections that generate lots of phlegm and snot are viral illnesses and will get better on their own, although you can expect to feel poorly for a few weeks. There are plenty of over-the-counter medicines which are very effective in managing the symptoms of these illnesses, and can reduce headache, muscle soreness, fever and sore throats.
The initial symptoms of a sinus infection are a green or yellow mucus discharge from your nose, accompanied by facial, often severe, pain around your cheeks, eyes or forehead. A viral infection is the most common cause of sinusitis. It's usually the result of a cold or flu virus that spreads to the sinuses from the upper airways. Around two-thirds of people with sinusitis don't need to see their GP. In most cases, the viral infection clears-up by itself, usually in about two-and-a-half weeks. If you have mild sinusitis, over-the-counter painkillers and decongestants will help relieve your symptoms. Seek medical advice if your symptoms don't improve after 7 days, if they are getting worse, or if your sinusitis keeps coming back. In such cases, antibiotics or a steroid spray or drops may be recommended.