Why Stomach Acid Attacks Eggshell
Eggshell is made mostly of calcium carbonate, the same mineral found in chalk and some antacid tablets. Stomach acid can react with calcium carbonate, breaking it down and releasing carbon dioxide gas. That fizzing reaction is easy to see if you put eggshell in vinegar, another acid.
Acid Does More Than Dissolve
In the stomach, hydrochloric acid helps unfold proteins and creates conditions that let digestive enzymes work. It does not simply melt everything on contact: how quickly a material breaks down depends on what it is made of, how much acid reaches it, and how long it remains in the stomach.
The useful comparison is chemical, not literal: materials rich in calcium carbonate are vulnerable to acid. That is why acidic liquids can wear away eggshell—and why the same mineral can help neutralize stomach acid when it is used in an antacid.
