Symptoms of small intestinal bacterial overgrowth, according to the SIBO Center for Digestive Health, include:

Bloating

Belching

Cramps

Constipation

Diarrhea

Heartburn (reflux or GERD)

Nausea

Food sensitivities

Headaches

Joint pain

Fatigue

Skin rashes

Respiratory symptoms (such as asthma)

Mood symptoms (such as depression)

Brain symptoms (such as autism)

Eczema

Steatorrhea (fatty stools)

Iron deficiency anemia

Flatulence

Abdominal pain

Vitamin B12 deficiency

 

Research from the University of Southern California published in the Journal of the American Medical Association indicated that the symptoms of SIBO were nearly universal to those symptoms associated with irritable bowel syndrome.

Source: 21 Symptoms of Small Intestinal Bacterial Overgrowth