@Julian Wong Hey Julian, yes taking certain antimicrobials such as oregano, Grapeseed extract will very likely negatively impact beneficial flora if taken for more than a few days at a time. Berberine, Neem and Allicin are a little less potent but more mixed - some studies show increased levels of beneficial flora others show slight decreases. Whilst herbs/ phenols and other compounds such as caprylic acid/ Monolaurin/ coconut oil, pomegranate husk, Quercetin, Lactoferrin, Mastic gum, black seed oil, EGCG and Chinese Skullcap are all much more safeguard antimicrobials and act more as mod biotics than wrecking balls for the microbiome. Most people should start with this approach first. I hope that helps!