Why is not recommended to use antibiotics often

If you take antibiotics for the wrong reason (s) or if you take them too often it can change bacteria so much, that antibiotics have a reduced effectiveness against them, or stop working against them all together.

The so called "bacterial resistance" or "antibiotic resistance" is a real thread to humans. Some bacteria have turned out to be resistant to even the most powerful antibiotics available. Antibiotic resistance is a growing problem.

Suppose you get infected with such resident bacteria, it means there is no longer an effective treatment by using antibiotics.

*EXTRA*

If left "un treated", the bacteria can grow, more or less, with unlimited exponential growth. In such scenarios, any "simple" bacterial infection, could turn out to be fatal.

Often the biggest problem is the lack of time to find out exactly what type of bacteria is making the patient ill. Because there are so many different bacteria, it is impossible to tell what is the right one without deduction and, that takes time (to grow visible cultures in the laboratory). Sometimes a patient might be already critically ill, in such cases, the doctor would want to start the treatment immediately, which could mean they HAVE TO start admitting a broad-spectrum antibiotic, to hopefully battle that group of different bacteria, which hopefully included the one that is making the patient ill. But if that specific bacteria turns out to be resestant, then that poses a very serious problem. Possible a fatal one, since the time is up, and the bacteria keep growing in numbers, roughly doubling in numbers every hour ...

Answer: It may cause the bacteria to become resistant to them and one they are resistant then the antibiotics are ineffective against the bacteria. It is then more dangerous since new antibiotics will need time.