Magnesium hydroxide [Mg(OH)2] is used as—

Magnesium hydroxide is a mild base and is commonly used as an antacid (anti-acid). It neutralizes excess hydrochloric acid in the stomach, providing relief from acidity and indigestion. It is the active ingredient in popular antacid medicines like Milk of Magnesia. It is not an oxidizing or reducing agent, nor is it used in fermentation.