Oral antihistamines (H1 receptor antagonists.Examples of topical intranasal antihistamines include olopatadine and azelastine .Combinations of antihistamines with decongestants .are effective when congestion is a feature of rhinitis, or when patients have no response or incomplete control of symptoms with intranasal corticosteroids.First-generation antihistamines, such as diphenhydramine and chlorpheniramine, are usually not preferred due to adverse effects, such as sedation, performance impairment, and other anticholinergic effects.The second-generation antihistamines (for example, fexofenadine, loratadine, desloratadine, cetirizine) are generally better tolerated.