A sore throat can be caused by an infection due to a virus or bacteria. Most of the time a sore throat is part of a viral illness like a cold. Less often, it can be due to a strep infection.
Antibiotics can cure strep throat because it is a bacterial infection.
However, antibiotics will not work for sore throats from colds or the flu. Here are signs of a strep throat. Sore throat, bright red tonsils, pus on the tonsils, fever, swollen glands in the neck. Sometimes kids can get a sandpaper-like rash. Kids with strep throat usually do not have other cold symptoms like runny nose and cough.