Patients are told they must finish their antibiotic prescription because they would otherwise increase their resistance to the drug. But the very reverse could be true, say researchers from Brighton and Sussex Medical School: it's taking antibiotics unnecessarily that increases resistance.

Lead researcher Martin Llewelyn says the advice to complete a course of antibiotics isn't supported by any evidence—and it's encouraging the rise of the 'superbugs' that can't be treated by the drugs.

Instead, the idea is born from a misplaced fear of under-treatment, but when the researchers looked at a range of common infections, they found that antibiotics were effective in around half the time that is routinely prescribed.

For instance, the ear infection, otitis media, can be successfully treated within five days, and yet the standard treatment time is 10 days. Similarly, the throat infection, streptococcal pharyngitis, needs just three to six days of treatment, and not the 10 days prescribed. Pneumonia needs just five days of antibiotics, again just half the time that's prescribed.

Doctors also adopt a one-size-fits-all approach to antibiotic prescribing, and treatment time can vary enormously from patient to patient. Antibiotics are a precious and finite resource, and doctors need to learn to change their prescribing habits, the researchers say.