Antibiotics: when they help and when they cost you

Antibiotics are among the most valuable medicines ever developed and among the most misused, and both facts follow from the same enthusiasm.

What they do and do not treat

Antibiotics act on bacteria and have no effect on viruses.

Which means they do nothing for colds, influenza, most sore throats, most coughs, most sinus symptoms in the first days, and most cases of gastroenteritis.

Green or coloured nasal discharge does not indicate bacterial infection, which is one of the most persistent misconceptions in primary care.

The duration of an ordinary cough after a viral infection is typically two to three weeks, which is longer than most people expect and is the reason many antibiotic courses appear to work.

Where they are clearly indicated

A defined set of situations.

Bacterial pneumonia.

Pyelonephritis and most symptomatic urinary tract infections.

Cellulitis and other skin infections.

Bacterial meningitis and sepsis, urgently.

Streptococcal throat infection in defined circumstances, assessed with scoring systems rather than by appearance alone.

Dental infection with spreading involvement, alongside dental treatment.

Certain sexually transmitted infections.

And prophylaxis in specific surgical and medical circumstances.

The costs of taking them unnecessarily

Individual as well as collective.

Side effects are common: diarrhoea, nausea, thrush and rashes.

Clostridioides difficile infection follows antibiotic use and can be severe, particularly in older adults.

Allergic reactions, some serious.

Disruption of the gut microbiome, with recovery over weeks to months and not always complete.

Interactions with other medicines.

And an increased likelihood that a future infection in the same person is resistant, which is a personal rather than an abstract consequence.

Resistance

The collective problem.

Antimicrobial resistance is estimated to be associated with a very large number of deaths globally each year, and the projections for coming decades are worse.

The mechanism is straightforward selection: exposure kills susceptible organisms and leaves resistant ones.

Which means each unnecessary course contributes marginally to a shared problem, and the aggregate is what makes routine surgery, chemotherapy and neonatal care riskier over time.

Agricultural use is also a substantial contributor and is regulated differently between countries.

Delayed prescribing

A practical middle route with good evidence.

The clinician provides a prescription with instructions to use it only if symptoms worsen or fail to improve by a specified point.

Trials show that a large proportion are never used, symptom outcomes are similar, and satisfaction is maintained.

Which makes it worth asking for where you are unsure, rather than pressing for immediate treatment or leaving with nothing.

Taking them properly

Where practice has shifted.

Take at the intervals prescribed, since blood levels matter.

Follow instructions about food, since some are affected by dairy, antacids or iron.

Complete the course as prescribed — with the note that the traditional message to always finish the course has been questioned, and that course lengths themselves have shortened for several indications as evidence has accumulated.

The practical position remains to follow the specific instruction given rather than to stop when you feel better or to extend the course.

Never save leftovers, never take someone else's, and never use a course left from a previous illness.

Return unused antibiotics to a pharmacy.

What to do instead for viral illness

Since the appointment still needs a purpose.

Symptomatic relief: fluids, analgesia, rest.

Honey for cough in adults and children over a year, which has evidence comparable to over-the-counter preparations.

Saline nasal irrigation for sinus symptoms.

Time, with a clear idea of the expected duration so that a normal course does not feel like deterioration.

And a safety net: knowing which symptoms mean returning, which is the genuinely useful output of the consultation.

The red flags

Where prompt antibiotics matter enormously.

Signs of sepsis: rapid breathing, confusion, mottled or discoloured skin, not passing urine, feeling extremely unwell.

Fever in a baby under three months.

Neck stiffness, photophobia and a non-blanching rash.

Rapidly spreading redness of the skin.

Severe abdominal or flank pain with fever.

Breathlessness and chest pain.

And any immunosuppressed person with a fever, where the threshold for urgent assessment is much lower.

General information only, not medical advice. Consult a qualified clinician about infections, seek urgent care for signs of sepsis, and never take antibiotics prescribed for someone else.