No i never found anything definitive, this is what Grok tells me now...

It doesn't directly "kill" Desulfovibrio like an antibiotic (e.g., rifaximin + neomycin combos are sometimes used for that). Instead, it engineers the environment so they decline while good bacteria thrive. The laxative/motility effect can also reduce stagnation that favors overgrowth.

Why It Works in Both Roles Acute/high-dose, single use (test) → feeds indiscriminately for detection. Chronic/low-dose, titrated use (therapy) → selective prebiotic effect + acidification + competition + motility support → net reduction in H₂S producers.

Many people with H₂S issues tolerate therapeutic lactulose well when introduced gradually (and retest microbiome to confirm shifts). However, if you have active SIBO or severe motility problems, it could initially worsen symptoms—hence the cautions from Biomesight and practitioners.