Oncet-3D Tablet is used to prevent asthma and treat allergic symptoms such as sneezing, runny nose, congestion, stuffy nose, or watery eyes. Asthma is a chronic (long-term) respiratory condition in which airways narrow, swell, and produce extra mucus, leading to difficulty in breathing. An allergy is a condition that occurs when the immune system reacts to a foreign substance that is typically not harmful to your body. These foreign substances are known as ‘allergens.’