Abstract–Part IBackgroundBlue light is emitted visible light between the wavelengths of 400 to 500 nm. The main source of blue light is sunlight, but digital screens, light‐emitting diodes (LEDs), and fluorescent lighting serve as additional sources. Concerns about the negative effects of blue light on the skin have rapidly increased over the past 15 years, and consequently, the urge to learn more about this topic is increasing as well.AimsPart I of this article provides up‐to‐date information on the definition of blue light and the negative and positive effects of blue light on the skin.MethodsAn Internet search was completed using the Google scholar database for relevant literature.ResultsBlue light can be both harmful and beneficial to the skin, depending on intensity and wavelength. Short‐term safety information is more readily available from clinical studies; however, the biological effects of repeated and/or longer‐term exposure are not fully understood yet.ConclusionsLow‐energy and low exposure times to high‐energy blue light can help prevent skin diseases, while studies have revealed that longer exposure to high‐energy blue light can increase the amount of DNA damage, cell and tissue death, and injury, eye damage, skin barrier damage, and photoaging.