The following is a summary of “Allergen immunotherapy effectively reduces the risk of exacerbations and lower respiratory tract infections in both seasonal and perennial allergic asthma: a nationwide epidemiological study” published in the November 2022 issue of Respiratory by Woehlk et al.

Infections and worsening of asthma symptoms in the respiratory system are more likely in those with allergic asthma. To what extent seasonal or perpetual allergies shape this vulnerability is still unknown. To examine whether or not allergen immunotherapy can mitigate the incidence of lower respiratory tract infections and asthma exacerbations in people with perennial allergy, as opposed to a seasonal allergy, allergen immunotherapy(AIT).   This study is a prospective, register-based investigation of AIT among U.S. residents aged 18 to 44 who received treatment between 1995 and 2014. Patients were classified as having either perennial allergic asthma (PAA) or seasonal allergic asthma (SAA) based on their AIT and medication use (SAA). 

Pre-AIT (baseline) and post-AIT (3 years later) antibiotic use against LRTI and use of oral corticosteroids for exacerbations were analyzed (follow-up).  Among the 2688 individuals with asthma treated with AIT, 1249 were diagnosed with PAA, and 1439 were diagnosed with SAA. More patients with SAA experienced exacerbations at baseline (23.8% vs. 16.5%, p≤0.001), but there was no difference in LRTI between the 2 groups. Researchers found that the number of exacerbations decreased by a statistically significant 57% in PAA and 74% in SAA during the course of the 3-year follow-up period.

Investigators also found that LRTI decreased significantly in both PAA and SAA, by 17% and 20%, respectively.  Both seasonal and perennial allergic asthma patients benefited from AIT, as it significantly decreased the likelihood of exacerbations and LRTIs. There is less evidence that perennial allergy poses a greater threat of respiratory infections and flare-ups than seasonal allergy does.