Background & Aims: To better understand the role of small intestinal bacterial overgrowth (SIBO) in rosacea, we aimed to assess the presence of SIBO in patients with rosacea and the clinical effectiveness of its eradication. Methods: We enrolled 113 consecutive rosacea ambulatory patients (31 M/82 F; mean age, 52 ± 15 years) and 60 healthy controls who were sex- and age-matched. Patients and controls underwent lactulose and glucose breath tests (BTs) to assess the presence of SIBO. Patients positive for SIBO were randomized to receive rifaximin therapy (1200 mg/day for 10 days) or placebo. A group of patients with negative BTs were also treated with rifaximin. Eradication was assessed 1 month after the end of therapy. Two dermatologists, unblinded on therapy, evaluated rosacea patients before and after treatment on the basis of an objective scale. Results: The prevalence of SIBO was higher in patients than controls (52/113 vs 3/60, P <.001). After eradication, cutaneous lesions cleared in 20 of 28 and greatly improved in 6 of 28 patients, whereas patients treated with placebo remained unchanged (18/20) or worsened (2/20) (P <.001). Placebo patients were subsequently switched to rifaximin therapy, and SIBO was eradicated in 17 of 20 cases. Fifteen had a complete resolution of rosacea. After antibiotic therapy, 13 of 16 patients with negative BTs for SIBO remained unchanged, and this result differed from SIBO-positive cases (P <.001). Conclusions: This study demonstrated that rosacea patients have a significantly higher SIBO prevalence than controls. Moreover, eradication of SIBO induced an almost complete regression of their cutaneous lesions and maintained this excellent result for at least 9 months.
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