Rhinitis and asthma in children: comorbitity or united airway disease?

The association of rhinitis with asthma symptoms in children is thought to be part of the united airway disease's theory which proposed three possible explanatory pathophysiological mechanisms: postnasal dripping, naso-bronchial reflex and systemic immune response. However, it is not clear if the relation is a co-morbid, precipitating or triggering condition or an epiphenomenon as an integrated part of the disease. In an attempt to evaluate the association, a review of all articles that were published in the last 10 years which referred to the relation of childhood rhinitis with asthma were analysed, whereas the recent knowledge on physiology and phenotype was reported as background. Even though both diseases share common etiology, epidemiology and immunology, there are important differences between the upper and lower airway system related both to inner organ cytology, immunity and heredity. Allergy seems to be the major causable factor for rhinitis and asthma association; however, ageenvironment interactions enhance the inspection that in preschoolers the diseases coexist, whereas in older children, they represent the manifestation of one united syndrome.