Dissolves metal but spares us: why hydrochloric acid doesn't burn through our skin (video).

The stomach is a biological center that regulates digestion, despite containing one of the most corrosive substances in the body: hydrochloric acid. This acid, with a pH of 0.8 in its pure form, is strong enough to dissolve metals. Nevertheless, the stomach lining remains intact, preventing self-digestion. This protective method has its unique origins and reasons, as noted by IFLScience.

This unusual protection of our stomach is provided by a robust mucus barrier, primarily composed of glycoproteins known as mucins. These mucins form a two-layered shield: a thick, stationary layer that adheres to the stomach walls, and a looser, gel-like layer where beneficial bacteria thrive.

Hydrochloric acid is secreted by the parietal cells of the stomach, and in combination with other secretions, it stabilizes the pH between 1 and 3, creating an environment ideal for food breakdown and the destruction of harmful microbes.

The mucus not only acts as a physical barrier but also contains bicarbonate—a substance that neutralizes the corrosive effects of the acid. This dual mechanism allows the stomach to perform its digestive functions without harming us. However, a disruption of this mucus protective layer can have serious consequences.

Some bacteria and parasites, such as Helicobacter pylori, can breach the mucosal barrier, leading to inflammation and severe gastric diseases. This vulnerability can result in the formation of ulcers, which in severe cases may cause internal bleeding or perforation of the stomach, leading to peritonitis—a life-threatening condition where acid seeps into the abdominal cavity.

Acid reflux, or heartburn, is a common condition that occurs when stomach acid escapes through the lower esophageal sphincter, causing discomfort and damaging the esophagus. Lifestyle factors such as smoking and alcohol consumption often exacerbate it.

To alleviate such symptoms, doctors typically prescribe medications containing bicarbonate, similar to the natural neutralizer found in gastric mucus. However, the acidic environment also fosters the development of a unique microbial ecosystem in the stomach. Beneficial gut bacteria residing in the looser layer of mucus play a crucial role in digestion and maintaining immune health, highlighting the balance that the stomach achieves in managing both digestive and protective functions.

This material is for informational purposes only and does not contain advice that may affect your health. If you are experiencing problems, consult a specialist.