Dr. Khan studies host–microbe interactions, focusing on how microbes drive or prevent disease, including cancer, allergies, obesity, and metabolic disorders. He examines how gut microbes shape the efficacy and bioavailability of oral Western and herbal medicines via host and microbial enzymes, and investigates causes of non‑response to oral drugs. Key findings include: a saponin anticancer pathway; far‑infrared–induced healing mechanisms; bacterial involvement in Kawasaki disease; icariin’s anti‑aging effects; and pregnancy‑linked microbiome shifts affecting newborns.