A: The vast majority of upper respiratory infections, colds and sore throats are caused by viruses. The importance of this is that they require only TLC, observation and no antibiotics.
The dangers of using unnecessary antibiotics cannot be overstated. If your child does not get better in a few days, has difficulty swallowing or develops a rash, a trip to his doctor is in order. Even then, in most cases, a throat swab is needed to make the diagnosis of strep (which is bacterial). If the culture is positive, an appropriate antibiotic for the right length of time should be given.
There is little danger in waiting 24 to 48 hours to begin treatment, but you do risk antibiotic resistance in giving unnecessary antibiotics.