Cutaneous adverse reactions (CARs) after COVD-19 messenger ribonucleic acid (mRNA) vaccines have been reported worldwide, but the pathophysiology of CARs remains to be elucidated. To understand the pathophysiology, it is essential to know how the innate and adaptive immunity are activated after vaccination. At present, majority of CARs are presumed to be evoked by innate immunity response. Reviewing the previous articles, I propose the clinical classification of CARs; local injection site reaction, generalized eruption, localized eruption and others. Since COVID-19 mutates continuously to overcome the existing vaccines, our steady efforts are indispensable to clarify the pathophysiology of CARs and contribute to the development of novel vaccines with least adverse events and high efficacy.