lactobacillus acidophilus liquid is made for/in the intestines, it's not made for/in the mouth. I don't know what good oral bacteria keeps bad oral bacteria in check.
like i said though EC cause could be a reaction to pathogens(germs/bacteria/airborne etc) because the immune system(good bacteria) in mouth or skin has been damaged, maybe by licking, picking, forceful peeling, bad oralhealth, hot water on lips etc could be any.