During the nursery and school season, a child waking up with thick, green discharge from the nose is one of the things parents worry about most. Many read green as "a germ has taken hold, antibiotics are needed". Yet mucus colour on its own does not show a bacterial infection. In this article we explain why the colour changes, what helps at home and when a check-up is needed.

Why does mucus turn green?

A cold usually starts with a clear, watery runny nose. The American Academy of Pediatrics (AAP) notes that over the following days the discharge becomes thicker and often coloured. The colour comes from white blood cells that gather in the nose to fight the virus, and from the greenish enzymes they contain. Because secretions build up overnight, the discharge usually looks greener in the morning. As the illness passes, it becomes thinner and clear again.

What does mucus colour mean?

  • Clear and watery: the first days of a cold, or allergy. If sneezing and itchy nose and eyes come with it, allergic rhinitis is considered.
  • White and thick: a blocked nose and thickening secretions.
  • Yellow or green: most often the normal change seen a few days into a cold. It does not need antibiotics on its own.
  • Streaked with blood: frequent nose-blowing and dry air can irritate the inside of the nose. If it keeps happening, see our article on nosebleeds.
  • Foul-smelling discharge from one side only: especially in young children, this suggests a small object pushed into the nose and needs an examination.

How long does it last?

According to the AAP, a typical cold slowly clears within 7 to 10 days; a runny nose and cough can continue for a while after the other symptoms. Discharge turning clear again after the yellow-green phase is a sign of recovery. The AAP advises contacting a doctor if, in a child older than 3 months, nasal discharge lasts longer than 10 to 14 days or a daytime cough lasts more than 10 days. In children who have just started nursery, colds can follow one another through the winter, so the runny nose may seem never to stop for weeks.

Are antibiotics needed?

Colds are caused by viruses, and the AAP stresses that antibiotics have no effect on viruses. The US Centers for Disease Control and Prevention (CDC) also states that most sinus infections are viral and many get better without antibiotics. Unnecessary antibiotics do not speed up recovery but increase the risk of side effects and resistance (antibiotic use in children). The decision is made by the doctor based not on mucus colour but on how long symptoms have lasted, how they have developed and the examination findings. With a long-lasting runny nose, sinusitis is part of this assessment.

What can be done at home?

  • Keep the nose clear: saline drops or spray soften the mucus; in small babies it can then be gently removed with a nasal aspirator (using saline drops).
  • Give more fluids: water, warm soup and, for breastfed babies, frequent feeds help keep secretions thin.
  • Teach nose-blowing: a school-age child should close one nostril at a time and blow gently; blowing hard can put pressure on the ears.
  • Watch the room air: rooms heated by radiators and stoves dry out the air. Do not overheat the room and air it regularly (what temperature should a baby's room be).
  • Keep away from smoke: nobody should smoke at home or in the car.
  • Do not start medicines yourself: over-the-counter decongestants and cold medicines are not recommended for young children; the doctor decides after an examination whether any medicine is needed.
  • Hygiene: throw tissues away straight away and wash hands with soap to reduce spread to siblings.

When is a check-up needed?

  • Any sign of illness in a baby younger than 3 months
  • A runny nose that lasts more than 10–14 days and is not improving
  • Symptoms that get better and then worse again, or a fever that starts later on
  • Fever lasting more than 3–4 days, ear pain or a feeling of fullness in the ear (fluid in the ear)
  • Swelling or redness around the eye, severe headache or facial pain
  • Foul-smelling discharge from one side only

Go to the emergency department without waiting if there is fast or laboured breathing, the skin pulling in below the ribs, bluish lips, inability to keep fluids down or unusual drowsiness.

Back-to-back colds through the winter do not mean an immune problem in most children (the child who is often ill). If the runny nose continues regardless of the season and comes with sneezing and itching, a paediatric allergy assessment is helpful. You can book an appointment at Özel Düztepe Yaşam Hospital in Şahinbey, Gaziantep.