Compositions containing both a sedative compound and a non-sedative antihistamine are provided. More particularly, compositions for administration at bedtime containing a sedating antihistamine or other sedating compound in immediate release form and a non-sedating antihistamine in delayed-release form are described. Alternatively, a composition, for administrating upon awakening, containing a non-sedating antihistamine in immediate release form, and a sedating antihistamine or other sedative in delayed-release form is described. Methods of inhibiting the release of histamines by administration of the compositions to a mammalian subject are also provided. The dosage forms may comprise other medications, such as leukotriene receptor antagonists, to enhance the suppression of histamine symptoms.