Yellow Snot: What It Means and When You Need Antibiotics

Quick answer

Usually a normal part of a cold; colour alone does not mean a bacterial infection

During a cold, mucus often starts clear and runny, then becomes thicker and yellow or green after a few days as white blood cells and their enzymes collect in it, before clearing again. This pattern is typical of viral infections and does not mean you need antibiotics. Bacterial sinusitis is more likely if symptoms last more than 10 days without improving, start to get worse after initially improving (“double worsening”), or are severe from the start with high fever and facial pain. Saline rinses, fluids, rest, steam and simple painkillers help most people. Green or yellow mucus with COVID-19 is also usually part of the viral illness.

Important. Seek urgent care for severe headache, swelling or redness around the eye, double vision or changes in vision, confusion, a stiff neck, high fever, or swelling of the forehead. See a doctor if symptoms last more than 10 days, keep getting worse or keep coming back.

Why snot turns yellow or green

Mucus is made constantly by the lining of the nose and sinuses. When a virus infects the lining, the body sends white blood cells called neutrophils to fight it. These cells contain a greenish enzyme (myeloperoxidase), and as more of them collect in the mucus it turns yellow and then green. The colour shows that your immune system is active, not which germ is responsible. Studies have shown that colour does not reliably distinguish viral from bacterial infections.

What different colours can mean

Clear: normal mucus, allergies or the start of a cold.
White or cloudy: congestion, a cold or dehydration.
Yellow: a cold or sinus infection in progress.
Green: more immune cells; common a few days into a cold.
Pink or red streaks: irritated or dry blood vessels from blowing the nose; see blood when blowing your nose.
Brown or orange: old blood, dust or smoke.
Black: heavy smoke or pollution exposure; rarely, a fungal infection in people with weakened immunity.

Cold or sinus infection?

Most colds last 7 to 10 days, with mucus changing colour along the way. Sinusitis means inflammation of the sinuses and most cases are also viral. Doctors suspect bacterial sinusitis when symptoms last longer than 10 days without improvement, when they improve and then worsen again, or when there is severe facial pain, high fever and thick discoloured mucus for several days at the start. Our guide to sinus infection symptoms explains the signs in detail.

How long does yellow snot last?

With a cold, yellow or green mucus often appears around days 3 to 5 and clears within 10 to 14 days.
A cough and some mucus can linger for up to three weeks.
Mucus that lasts more than three to four weeks may indicate chronic sinusitis, allergies, nasal polyps or another problem.
In young children, coloured snot is very common and usually part of repeated viral colds.

Home remedies

Saline sprays or rinses: clear mucus and reduce congestion; use boiled and cooled or sterile water.
Fluids: keep mucus thin.
Steam: a hot shower or warm, humid air.
Rest and sleep with your head slightly raised.
Painkillers: paracetamol or ibuprofen for aches and fever, if suitable.
Decongestant sprays for no more than three to five days.
Blow gently, one nostril at a time, to avoid pressure in the ears.

When are antibiotics needed?

Antibiotics do not help colds or viral sinusitis and can cause side effects such as diarrhoea and allergic reactions, as well as contributing to antibiotic resistance. Guidelines recommend considering antibiotics, or watchful waiting with a plan to start them, for adults with likely bacterial sinusitis based on the pattern of illness rather than mucus colour. In many cases a doctor will advise waiting a few more days if you are not very unwell.

Green or yellow mucus with COVID-19 and flu

COVID-19 and flu can cause a runny nose with coloured mucus, along with fever, cough, aches, tiredness and sometimes loss of smell. Colour does not tell you which virus you have. Testing, if available, and local health advice help decide what to do. Most people recover at home; seek medical help if you are breathless, have chest pain or are in a high-risk group.

Three common situations

Day four of a cold with green snot: this is expected; carry on with rest, fluids and saline, and expect it to clear over the next week.
Twelve days of thick mucus, facial pain and no improvement: see a doctor; bacterial sinusitis is possible.
Toddler with constant yellow snot at nursery: repeated viral colds are normal in young children; see a doctor if they have high fever, ear pain, breathing difficulty or seem unwell.

How to avoid catching colds

Wash your hands often with soap and water, especially before eating and after blowing your nose.
Avoid touching your eyes, nose and mouth with unwashed hands.
Use tissues once and throw them away.
Keep up with recommended flu and COVID-19 vaccines.
Sleep well, stay active and avoid smoking, which damages the lining of the nose.
Children catch many colds as their immune systems develop; frequent colds in early childhood are normal.

Key points to remember

Yellow or green snot is a normal sign of an immune response.
Colour alone does not mean you need antibiotics.
Most colds clear in 10 to 14 days.
See a doctor for symptoms lasting over 10 days, worsening or warning signs.

Questions about yellow snot

These answers are general information and do not replace an examination or individual medical advice.

Does yellow snot mean I am contagious?

You are usually most contagious in the first few days of a cold, often before mucus turns yellow. Wash hands often and cover coughs and sneezes.

Is green snot worse than yellow?

Not necessarily. Green mucus simply contains more immune cells. It does not mean the infection is bacterial or more serious.

Why is my snot yellow in the morning only?

Mucus collects overnight and becomes thicker and darker. Clear or white mucus later in the day is common with allergies or postnasal drip.

Can allergies cause yellow mucus?

Allergies usually cause clear, watery mucus. Yellow or green mucus suggests a cold or infection, sometimes on top of allergies.

How can I get rid of yellow mucus fast?

Saline rinses, fluids, steam and rest help clear it. There is no quick cure for a cold, but symptoms usually improve within a week or two.

Sources

This guide is for general information and does not replace medical advice. How a problem is diagnosed and treated depends on your examination and medical history. If you think you have an emergency, contact your local emergency services.