Which of the following describes a characteristic of an antacid?

Antacids are compounds that are specifically formulated to help neutralize stomach acid. They are commonly used to relieve symptoms associated with excessive stomach acid, such as heartburn, indigestion, and upset stomach. By increasing the pH level in the stomach, antacids can provide quick relief from discomfort caused by acid reflux or gastritis.

The other options do not accurately reflect the primary function of antacids. Increasing acidity in the stomach is contrary to the purpose of antacids, which aim to reduce acidity. While some medications can be used to address allergies, antacids are not among them. Additionally, while antacids may indirectly aid digestion by alleviating discomfort that can interfere with the digestive process, their main role is not to aid in digestion directly but to reduce acidity. Thus, the correct characterization of antacids is that they help neutralize stomach acid.