Antibiotics are among the most important medicines ever discovered, turning once-deadly infections into manageable illnesses. But they are also widely misunderstood and frequently misused. Knowing how antibiotics work, and why resistance has become one of the biggest threats in modern medicine, helps you use them wisely and protect both yourself and your community.
What antibiotics actually do
Antibiotics target bacteria. Some kill bacteria outright by destroying their cell walls; others stop them from multiplying so your immune system can finish the job. Different classes, such as penicillins, cephalosporins, macrolides, and tetracyclines, attack bacteria in different ways, which is why doctors choose specific antibiotics for specific infections.
The key point
Antibiotics work only on bacteria. They do nothing against viruses, which cause most coughs, colds, sore throats, and the flu.
Why they won't help your cold
Because colds and flu are viral, taking antibiotics for them brings no benefit and real downsides: side effects like diarrhoea and rashes, disruption of your healthy gut bacteria, and a contribution to resistance. A clinician can help distinguish a viral illness that will pass on its own from a bacterial infection that genuinely needs treatment.
What antibiotic resistance means
Every time bacteria are exposed to an antibiotic, the most vulnerable ones die, but any that happen to survive can multiply and pass on their resistance. Over time, and accelerated by overuse, this produces bacteria that our existing antibiotics can no longer kill. These resistant infections are harder to treat, require stronger or longer treatment, and can be dangerous. Resistance is now a leading global health concern recognised across the US, UK, EU, and Canada.
How to use antibiotics responsibly
- Only take antibiotics prescribed for you by a clinician, never leftovers or someone else's.
- Take them exactly as directed, at the right times.
- Complete the course as advised, or follow your clinician's specific guidance if they tell you otherwise.
- Never pressure a doctor for antibiotics for a viral illness.
- Never share antibiotics or save them for next time.
Seek urgent help
If an infection causes a high fever, confusion, a rash that does not fade under pressure, difficulty breathing, or rapidly spreading redness, seek emergency care immediately. Call 911 (US/Canada), 999 (UK), or 112 (EU).
Managing common side effects
Stomach upset and diarrhoea are common because antibiotics affect gut bacteria too. Taking some antibiotics with food can help, though others should be taken on an empty stomach, so always check the label or ask your pharmacist. Persistent or severe diarrhoea should be reported to a clinician, as it can occasionally signal a more serious problem.
Used correctly, antibiotics remain lifesaving. Used carelessly, they lose their power for everyone. If you are unsure whether your illness needs an antibiotic, a licensed doctor on iHealix can assess your symptoms and advise the right course, including when no antibiotic is the best medicine.
This article is informational only and does not replace advice from a qualified healthcare professional.