You can die
If left untreated.
you explode
It depends on what and how debilitating it is
If not treated the person can die and infect others as well.
untreated strep throat
He would be in a bad predicament.
An untreated infection may spread to the lymphatic system (acute lymphangitis ), the lymph nodes (lymphadenitis ), the bloodstream (bacteremia ), or into deeper tissues.
It can become a problem beacuse it may lead to other stuff such as, cough, fever, vomit,etc
Untreated, the scarlet fever can cause death.
flea infestation can cause a puppy to develop anemia and die if left untreated
It will burn the lining of the mouth, throat, esophagus and stomach. If left untreated, you will be in agony until you finally die.
millions of people will be left untreated and maybe die and we have an economic collapse.