Olozest 5mg Tablet is an antihistamine medicine used in the treatment of allergic rhinitis, hives, and itching associated with skin diseases. This medicine contains olopatadine which works by inhibiting the action of histamine, a chemical messenger responsible for causing allergies. It helps relieve congestion, itching, redness, sneezing, and runny nose. Some of the common side effects include nausea, headache, rashes, and itching.