Hi Chris recently on the internet I came across this study which was called “cohabitation – relationships of Corynebacteria and staphylococci on human skin”. That study says that staphylococci aren’t much affected by changing PH value from 3.5-6 while growth of corynebacteria was significantly inhibited if the ph was below 6. They used lactic acid, HCl and propionic acid at ph value of 6, 5.5 and 5 each. Lower the ph value less corynebacteria was able to grow and at 5 PH corynebacteria weren’t able to grow at all in case of all 3 acids. I know that HCl and propionic acid are very dangerous for human skin but lactic acid is widely used as skin care product maybe it’s good idea to apply lactic acid in the underarms? I’m pretty sure you already know this study I would like to hear your thoughts on it if not you should check it out. Also I know that bacteria in deeper skin layers are the main problem but if one managed to “fix” the microbiome on epidermis wouldn’t the good bacteria regain dominance in the deeper skin layers as well? Would changing the ph by applying certain acid topically affect bacteria inside the skin?