A commonly used antifungal medication may help ease inflammatory bowel disease symptoms in some patients by restoring a healthier gut microbiome, according to a new prospective observational study from Weill Cornell Medicine. The findings, published on September 1, 2026 in Nature Medicine, add to growing evidence that fungi in the gut may play an active role in disease progression rather than simply appearing as bystanders.
The IVAN study, short for IBD Therapy Via Antifungal-driven Microbiota Normalization, enrolled 53 patients with mild-to-moderate Crohn’s disease or ulcerative colitis who also had mild oral thrush and were receiving routine care at Weill Cornell Medicine and the Jill Roberts Center for Inflammatory Bowel Disease at NewYork-Presbyterian/Weill Cornell Medical Center. Researchers compared two antifungal approaches: fluconazole, which works systemically throughout the gastrointestinal tract, and nystatin mouthwash, which acts locally in the mouth.
Why the study matters for precision IBD care
Patients who received fluconazole, but not the oral nystatin wash, experienced improved IBD symptoms and a healthier gut microbial community after treatment. The study reported increased bacterial diversity, enhanced butyrate production and improved clinical disease activity in the fluconazole group, suggesting that reducing intestinal Candida burden may help restore microbial balance in selected patients.
According to the researchers, the work provides what is thought to be the first evidence that targeting intestinal fungal dysbiosis can reshape bacterial and fungal microbiome dynamics in people with IBD. The study also supports the idea of mycobiome-guided precision therapies, where treatment could eventually be tailored to the microbial profile of individual patients.
Fungal signals may influence disease pathways
The research builds on more than a decade of work from Dr. Iliyan D. Iliev’s laboratory on how fungal organisms in the gastrointestinal tract interact with the immune system and the gut microbiota. The team has previously shown that some patients with IBD and related conditions have an intestinal overgrowth of Candida albicans, and that related fungal strains can be shared between the mouth and the gut.
That observation helped shape the study design, because a simple cheek swab could reflect the fungi present in the gastrointestinal tract. By focusing on patients with thrush, the researchers were able to test whether clearing fungal overgrowth might translate into improvements in intestinal symptoms and microbial health.
Dr. Iliev said the findings highlight the potential of microbiome-based approaches to restore balance in the gut and noted that reducing intestinal Candida burden was associated with recovery of some beneficial bacteria and improvements in clinical disease activity. The authors caution that further research is needed before the findings can be translated into routine treatment decisions, but the study points to a possible new therapeutic direction for a subset of patients with IBD.
Related report and published study context.
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