Childhood wheezing may protect against future allergy

Young children who wheeze from time to time (so-called early transient wheezers) are less likely to develop allergy in adolescence than their peers who never or only infrequently wheeze, according to a study conducted in Australia. Children with persistent wheeze, on the other hand, are at increased risk of having other allergic manifestations in later childhood and adolescence, researchers found.

The study was conducted in a longitudinal birth cohort of 620 children from families with a history of allergic disease, who were followed up to the age of 18 years. Researchers identified 5 wheeze patterns these children exhibited from the age of 4 weeks to 7 years: never/infrequent (47%), early transient (26%), early persistent (5%), intermediate onset (19%), and late onset (3%). Investigators collected data about participants’ wheezing 18 times in the first 2 years of life. They also conducted skin prick testing for common allergens at ages 6, 12, and 24 months and 12 and 18 years, measured fractional exhaled nitric oxide (FENO), a determinant of eosinophilic airway inflammation, and collected information about the existence of eczema and hay fever.

Analysis of the collected data, which took into account potential confounders, including sociodemographic factors and parental smoking and asthma, showed that compared with never/infrequent wheezers, early transient wheezers had reduced risks of hay fever and eczema at age 18 years, along with lower FENO levels and lower risk of sensitization. In contrast, both intermediate onset and late onset wheezers were at increased risk of having hay fever at 12 and 18 years of age, compared with never/infrequent wheezers, with youngsters’ having the intermediate onset pattern also at increased risk of sensitization and higher FENO levels. Although early persistent and intermediate onset wheezers were at increased risk of eczema at 12 years, no wheeze pattern was associated with eczema at 18 years. Overall, intermediate onset wheezers represented the most atopic group (Dodge CJ, et al. Pediatr Allergy Immunol. 2020; Epub ahead of print).

Thoughts from Dr Farber

This impressive, very long-term study provides some indirect evidence for the ‘hygiene hypothesis,’ that early exposure (in this case, perhaps to respiratory viruses) helps protect against allergies. It would have been nice to see if early transient wheezers were less likely to have asthma when older.