Small Intestinal Bacterial Overgrowth (SIBO) and Small Intestinal Fungal Overgrowth (SIFO) are conditions in which bacteria or yeast grow excessively in the small intestine, where they’re normally limited.

These overgrowths can cause symptoms like bloating, gas, abdominal pain, and changes in bowel habits. In people with CIRS or other environmentally-triggered illnesses, SIBO/SIFO may develop as a secondary issue due to impaired immune regulation, slowed motility, or microbiome disruption.

While treatment often involves medical management, nutrition plays a key supportive role. A low-FODMAP diet—removing fermentable fibers that feed overgrown microbes—can reduce symptoms and support recovery. This is typically a temporary strategy followed by gradual reintroduction and microbial restoration.

SIFO management may involve reducing sugar and refined carbs, which fuel yeast overgrowth, while incorporating antifungal foods like garlic, oregano, and coconut oil. As symptoms improve, rebalancing with fiber-rich and fermented foods is essential to prevent recurrence.