Which conditions are antihistamines used to treat?

Antihistamines are primarily used to treat conditions related to allergic reactions, and one of the most common conditions they address is urticaria, also known as hives. Urticaria occurs when histamine is released from mast cells, leading to the characteristic red, itchy welts on the skin. By blocking histamine receptors, antihistamines effectively alleviate itching, reduce swelling, and provide relief from discomfort associated with this condition.

In contrast, other options such as heart failure, hypertension, and gastroesophageal reflux disease (GERD) do not involve histamine-related pathways and are treated with different classes of medications specifically designed for those conditions. Hence, antihistamines are not indicated for those conditions.