Clearing up Fungal infection with vinegar

My daughter had this dark mark on her neck.  We didnt really notice it getting bigger, it just suddenly seemed to be there.  It happened in September and my first reaction was that it had to do with sunburn or too much sun exposure.  But then it never went away and didnt peel like sunburn.  It was sort of speckled, and it never itched or bothered her.  After a couple of weeks our pediatrician saw it and thought it looked like a fungal infection and recommended an over the counter anti-fungal ointment. 

However I have always heard that vinegar is a great natural remedy for fungus, so we tried using apple cider vinegar on her neck twice a day.  I would soak a paper towel and wipe her neck with it.  She hated the smell, and put up a little bit of a fuss for this treatment.  However within two days it was completely gone. 

I treated her for another day, but there was no sign of it and it never returned.