Coldout Tablet works by the combined effect of its three components. , Dextromethorphan is a cough suppressant, it acts on a specific part of the cough centre or brain and reduces the formation of cough. , Phenylephrine is a nasal decongestant. It works by reducing the swelling of blood vessels of nasal passage by constricting the blood vessels and thereby relieving nasal congestion or blockage and making breathing easier. , Chlorpheniramine is an anti-allergic agent. It helps in relieving symptoms of allergy. It works by blocking the action of the natural substance histamine, which is responsible for allergic symptoms.