Antibiotics do not have an effect on all diseases
Antibiotics won’t cure you when you have the flu, a cold, acute bronchitis or most forms of laryngitis and otitis. Why not? Because these infections are caused by viruses. Antibiotics only help when you have a disease that is caused by bacteria. Learn more about bacteria and viruses.
Usually, we get better spontaneously after a few days. Our body produces specific antibodies to kill the intruders. That is how our immune system is built up.
Pneumonia and bacterial meningitis are caused by bacteria. Of course, antibiotics will be needed to deal with such severe infectious diseases.