Histan 4mg is an antihistamine medication containing chlorpheniramine maleate used to treat allergy symptoms such as sneezing, runny nose, itching, watery eyes, and rashes. Each pack contains 20 tablets of 4mg strength. This medication should be taken as directed by your healthcare provider. Common side effects may include drowsiness. Do not take if you are allergic to chlorpheniramine maleate or any ingredients. Consult your doctor before use if you have medical conditions or are taking other medications. Keep out of reach of children and store at room temperature. A prescription may be required for purchase.