Chronic cough is usually descibed as the cough lasting more than 4 wk [11] and is associated with high morbidity in children and their families. The prevalance of chronic
cough is 22 % in children [11]. The causes of chronic cough in children vary depending on age. In preschoolers with chronic cough, the most common cause was persistent bacterial bronchitis (40 %). The next most common cause was prolonged upper respiratory tract infection (URTI), while only 10 % of cases were caused by asthma, upper airway cough syndrome or gastroesophageal reflux disease. In school children,the most common causes of chronic cough were asthma(25 %), persistent bacterial bronchitis (23 %), upper airways syndrome (20 %) and gastroesophageal reflux disease (5 %) [11]. Inflammatory processes of the respiratory tract are associated with up regulation of both cough hyperactivity and bronchial hyperactivity and may lead to asthma or are associated
with chronic cough. In recent decades, the prevalence of recurrent infections and chronic cough have been steadily increasing[12]. However, quite a few data are available on the effect of vitamin D therapy in recurrent infections and chronic cough cases with low serum vitamin D levels