An initial experimental study was carried out with the hypothesis that one possible explanation for the low prevalence of asthma and other allergic diseases in Covid-19 patients could be a reduced angiotensin-converting enzyme-2 (ACE2) gene expression in the airway cells of these patients (Jackson et al., 2020), but another experimental study has found opposite results (Sajuthi et al., 2020). This evidence concerns the gene ACE2 and allergic disease.