The infant and toddler with wheezing.

Recurrent wheezing is common in young infants and toddlers, with 50% of all children having at least one wheezing episode in the first 6 years of life. Initial wheezing episodes in young children often are linked to respiratory infections due to viral pathogens, such as respiratory syncytial virus, human rhinovirus, human metapneumovirus, and influenza virus. Bacterial colonization of the neonatal airway also may be significant in the late development of recurrent wheeze and asthma. Wheezing in young children can be classified into specific phenotypes based on the onset and persistence of wheezing. Although some children will only wheeze transiently in early childhood, persistent wheezing is often classified as immunoglobulin E (IgE) associated and/or atopic or nonatopic. By using a modified asthma predictive index, future development of asthma can be interpreted, especially in high-risk populations. It is recommended to follow National Asthma Education and Prevention Program (NAEPP) guidelines for initiation of treatment; however, asthma management of young children often requires tailored regimens. Inhaled corticosteroids used as a daily controller medication have been shown to aid symptoms and exacerbation control; however, these do not change the natural course of the disease or progression to asthma. Although randomized double-blind studies in preschoolers investigated a role of macrolide antibiotics in early infection as well as high-dose inhaled corticosteroids during severe lower respiratory tract infections, more research is needed in this field to understand mechanisms of asthma development and optimal treatment in this young age group.