Asthma, allergies and COVID-19: a review of what we know

Introduction: Allergies are exaggerated reactions of the immune system to normally harmless substances, while asthma is a chronic disease that inflames the airways. Although people with asthma may be more susceptible to respiratory infections, the relationship between COVID-19 and asthma and allergies is contradictory and a matter of debate. Objective: To summarize the theoretical background on the relationship between allergic diseases, such as asthma, and COVID-19. Development: There is no conclusive evidence on the relationship between asthma, especially the allergic phenotype, and COVID-19. However, several aspects of immunopathogenesis may influence this interaction. The type I interferon response in asthmatics does not seem defective, and ACE2 underexpression could slow down the infection, allowing an adequate antiviral response. Eosinophils, which protect against viral infections, could compensate for the eosinopenia observed in COVID-19. The elevated presence of Th2 cells in asthmatics could also offer protection against severe forms of the disease. Despite this, asthma can predispose to severe symptoms due to inflammation and changes in the respiratory microbiota. Conclusions: The relationship between asthma, allergies and COVID-19 is complex and subject to debate, influenced by multiple factors. Additional studies are needed to better understand these interactions and the genetic and environmental factors that may affect the prevalence and response to these diseases.