Allergy, cold, and sinus medicines are over-the-counter drugs designed to relieve symptoms associated with allergies, colds, and sinus infections. These medicines typically come in various forms, including pills, liquids, nasal sprays, and more, and contain different active ingredients that work to alleviate specific symptoms. Antihistamines are a common type of allergy medicine that works by blocking histamine, a chemical released by the body in response to allergens. Histamine can cause symptoms such as itching, sneezing, and runny nose. Antihistamines are available in various forms, including pills, liquids, and nasal sprays, and can relieve allergy symptoms.