It is widely recognized that tobacco smoke causes skin pigmentation. No studies, however, have directly evaluated the mechanisms of the changes in smoker's skin pigmentation. In this study, when cultured with water‐soluble tobacco smoke extract, the human epidermal melanocytes grew to a large size and produced more melanins. We evaluated melanocyte activation by quantifying microphthalmia‐associated transcription factor (MITF) expression by real‐time polymerase chain reaction. MITF expression was significantly and dose‐dependently increased by exposure to tobacco smoke extract. The Wnt/β‐catenin signalling pathway seemed to mediate the tobacco smoke extract–induced melanocyte activation. Immunocytochemical studies revealed that the activated melanocytes actively expressed aryl hydrocarbon receptors (AhR) around the nuclear membrane. The tobacco smoke extract–induced MITF activation was inhibited by RNA silencing of the AhR. This study provides the evidence that tobacco smoke enhances pigmentation in vitro and that the increase in pigmentation may involve β‐catenin‐ and AhR‐mediated mechanisms inside human melanocytes.

• COVID-19 is associated with specific skin manifestations and drug eruption. • This case shows COVID-19–related drug eruption and specific clinical features. • Drug eruption preceding COVID-19 symptoms may facilitate early diagnosis.