BMJ Group Medical Reference
Antibiotics are medicines that kill bacteria. They don't work against viruses, which are the most common cause of sore throats. Antibiotics may help if you have strep throat (a sore throat caused by bacteria called Streptococcus).
There are lots of different antibiotics. Amoxicillin and erythromycin are two that doctors commonly prescribe.
Antibiotics can cut the time you have a sore throat for by about one day.  They can also reduce the risk of complications such as rheumatic fever, an ear infection, or an abscess on the tonsils.  But rheumatic fever and abscesses are very rare anyway.
Most doctors are careful not to prescribe antibiotics unless they think you really need them, as antibiotics may not work as well in the future if they are used too much. This is because bacteria can become resistant to antibiotics.
Antibiotics can also cause side effects such as an upset stomach, diarrhoea, and a rash. 
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