Allergic asthma is a chronic inflammatory lung disease characterized by eosinophilic airway inflammation, mucus hypersecretion and airway hyperreactivity in response to inhaled allergens, causing narrowing of the airways. Viral respiratory tract infections by influenza virus (INF), respiratory syncitial virus (RSV) and Rhinovirus (RV) have been implicated in causing allergic sensitization and the development of asthma, although their exact role remains controversial. In established asthma, respiratory virus infection are a frequent cause of disease exacerbation. Despite the fact that viral in infection influence the immune system in completely different ways at different time points in the asthma pathogenesis, it is clear that they can have a great influence on the course of asthma . The role of viral respiratory tract infections in the induction of asthma has been suggested. Epidemiological studies have shown that severe viral lower respiratory tract (LRT) infection during the first years of life are associated with an increased risk of developing asthma in children Although lower respiratory tract infection and brochiolitis caused by RSV poses a risk factor for subsequent wheezing and impaired lung function in early childhood, in most children postbronciolitic wheezing resolves by 13 years of age Eight seven percent of children who had active asthma between the age of 5 and 11 years had lower respiratory symptoms before the age of 5.