They may have som bad side effects such as nausea, indigestion, vomiting etc. Also the bacteria change or adapt if not taken correctly so they are no longer affected by the antibiotic.
Some doctors are pressured to give a patient antibiotics even if the patient has a viral infection which will be unaffected by the antibiotic; sure, it’ll fight off bacterial infections, but if not taken correctly, and most importantly to look out for in the long run is antibiotic resistance - which is when the bacteria mutate and will be immune to the antibiotic you’re taking and that mutated cell will multiply. Eventually, you’ll need stronger and stronger antibiotics; therefore, it’s best to only use when it’s necessary!
