Stomach acid is strong enough to dissolve many things that people accidentally swallow.

The longer version

Hydrochloric acid in the stomach is produced by specialised cells in the stomach lining, and it creates a very low pH environment. That acidity unfolds the tangled proteins in food so digestive enzymes can cut them apart more easily, and it kills or weakens a large share of the microbes that arrive with a meal.

The stomach protects itself with a thick layer of mucus and with bicarbonate that neutralises acid right at the cell surface. Without that barrier, the lining would digest itself. Acid production rises when food is expected, since the sight and smell of a meal already start the signal. The same corrosive quality is why swallowed non-food objects can be altered by long contact with stomach contents.

Where this entry sits

These facts look at how the human body works in ordinary moments, from breathing and blinking to balance and sleep. They focus on anatomy, senses, and small reactions that happen constantly without any conscious effort. The full list sits on the Human Body page, where every entry is listed in order.