The present invention relates to a method for treating a behavior disorder comprising the administration of a therapeutically effective amount of antihistamine, such as ceterizine, fexofenadine; loratadine, and desloratadine. The behavioral disorders may include ADHD, anxieity, depression, and autism. The method may include the administration of the antihistamine in combination with a stimulant medication, such as methylphenidate, thereby to achieve a synergistic effect. In any event, the amount of antihistamine and/or stimulant is effective to downregulate neurotrophic factors such as nerve growth factor or CD40. The invention is also directed to a method of preventing the onset of behavior disorders in patients presenting with symptoms of allergic rhinitis.