Allegra-D Tablet 10's is used to treat symptoms such as sneezing, a runny or blocked nose, itchy or watery eyes, hives, skin rashes, itching, and other allergy or cold-related symptoms. It inhibits histamines to alleviate allergy symptoms and decreases nasal swelling, which helps clear congestion and enhance breathing. In some cases, this medicine may cause side effects such as headache, nausea, dry mouth, stomach discomfort, insomnia and dizziness.