Clemastine Fumarate is primarily used as an antihistamine to relieve allergy symptoms such as sneezing, runny nose, itching, and watery eyes. It is effective in treating allergic conditions like hay fever, hives, and other skin reactions. Additionally, it can be used to alleviate symptoms of the common cold by reducing nasal congestion and sinus pressure. In some cases, it is also prescribed to manage mild cases of insomnia due to its sedative properties. This medication works by blocking histamine, a substance in the body that causes allergic symptoms, providing relief for individuals suffering from various allergic reactions.