Colds and flu

Updated 27 August 2019

My phlegm is yellow, do I need antibiotics?

Does the colour of your phlegm really indicate whether you should be on antibiotics, or is this yet another myth?

Coughing and wheezing, sniffles and sneezing are all symptoms of a cold, flu or even a sinus infection.

These symptoms may leave you feeling down and lousy. Over-the-counter medication may have not eased the symptoms… Need something stronger?

Well antibiotics may do the trick, but this all depends on what you have. Taking an antibiotic particularly for a cold can be a problem, thanks to the common misconception that antibiotics can treat all types of infections.

According to a survey done by the World Health Organization, two thirds of South Africans think that antibiotics are effective for colds and flu. 

Antibiotics are only active against bacteria. Colds and flu are caused by viruses against which antibiotics have no effect. The more antibiotics you use, the higher your chances of developing resistant bacteria.

Cold vs. flu 

There’s a difference between a cold and flu.

Yes, they’re both respiratory illnesses but are caused by different viruses. Upper respiratory infections like colds and influenza are caused by a virus.

Antibiotics only kill bacteria. With viruses, you generally need a vaccination to prevent them and antiviral medication to treat them.

Your doctor can prescribe this for you and will help you figure out if it’s a viral or bacterial infection. In essence, antibiotics will kill both good and bad bacteria and leave your body even more vulnerable to infections.

Phlegm 101 

When you have a cold, you may produce yellow phlegm. This doesn’t need antibiotics. 

Yellow phlegm: Your body is fighting off an infection or virus or you could be getting sick. 

Green phlegm: Your immune system is fighting back the infection. If the colour persists for more than a week or you develop a fever, check with your doctor.

So, do you need an antibiotic? 

According to the Center for Disease Control and Prevention, antibiotics can do more harm than good.

Remember, taking antibiotics increases your risk of developing an antibiotic resistance infection later; which is a result of taking antibiotics for the wrong reasons and when they haven’t been prescribed to you.

They also kill the healthy bacteria in the gut, allowing more harmful bacteria to grow in its place. Your doctor will prescribe antibiotics if he thinks it’s necessary.

This will be followed with either a short- or long-term course of your antibiotic intake and clear instructions to finish your course regardless of if you’re feeling better.

Treat a bacterial infection right away

  • Act quickly. Begin treatment at the first sign of infection.
  • Change your diet. Eliminate sugar that could feed pathogenic bacteria.
  • Get two times as much good bacteria in your diet (probiotic foods). This will build up a healthy immune response.
  • Get enough rest to boost your immune system.
  • Drink plenty of fluids to help you replace those you’ve lost.

Image credit: iStock


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Dr Heidi van Deventer completed her MBChB (Bachelor of Medicine and Bachelor of Surgery) degree in 2004 at the University of Stellenbosch.
She has additional training in ACLS (Advanced Cardiac Life Support) and PALS (Paediatric Advanced Life Support) as well as biostatistics and epidemiology.

Dr Van Deventer is currently working as a researcher at the Desmond Tutu Tuberculosis Centre at the University of Stellenbosch.

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