Can stomach acid dissolve fish bones?

Whether gastric acid can corrode a fish bone depends on the size of the bone.

Fish bones are essentially fish vertebrae, primarily composed of calcium. If a small fish bone is accidentally swallowed during a meal, it typically reaches the stomach and is gradually dissolved by the strong acidic environment. Some of the bone may be converted into absorbable calcium compounds and subsequently absorbed through the duodenum and small intestine. The remaining fragments become dietary residue and are excreted naturally in the feces. This process occurs mainly due to a chemical reaction between gastric acid and calcium carbonate; therefore, concerns about gastric mucosal injury, bleeding, or erosion caused by small fish bones are generally unwarranted.

However, if a relatively large fish bone is accidentally swallowed, it may perforate the esophagus or stomach wall and potentially lead to diffuse peritonitis, resulting in intra-abdominal infection or abscess formation. In such cases, gastric acid is insufficient to dissolve the bone. Once this occurs, patients should refrain from eating and promptly seek evaluation at an otolaryngology (ENT) department. Under endoscopic guidance, the fish bone can be safely removed from the esophageal or gastric mucosa to relieve symptoms.