H2 antihistamines are a class of medications primarily used to reduce stomach acid production. They work by blocking the action of histamine, a substance in the body that stimulates acid secretion in the stomach. Commonly prescribed for conditions like gastroesophageal reflux disease (GERD) and peptic ulcers, these medications help alleviate symptoms such as heartburn and indigestion. Unlike H1 antihistamines, which are used to treat allergies, H2 antihistamines target the stomach's histamine receptors. Some well-known examples include ranitidine and famotidine. These drugs are generally considered safe and effective, but they may have side effects, including headaches and dizziness. Always consult a healthcare professional before use.