For this review, we have undertaken a comprehensive search through MEDLINE, EMBASE, Scopus, LitCovid and Web of Science using the following keywords: circadian clock disruption, COVID‐19, SARS‐2, angiotensin‐converting enzyme (ACE)/angiotensin‐converting enzyme 2 (ACE2), Clock Genes, Epithelium, Immunity, Infection, Chronotherapy, Sex differences, Microbiome and Melatonin. The gene discussed is ACE; the disease is COVID-19.