No in general terms the light emitted by the barcode scanner isn't harmful to people be it the skin or any other body part. But in the case of the light affecting the eyes is a whole different case. As the eyes of humans are a sensitive area. And is advised to keep away from contact with the eyes. The flashing of the light in this area might not cause damage as such. As it is a human reflex to divert the eyes from the beam. But you also have to consider the cases of people who wear prescribed contact lenses. This could magnify the beam of light which in turn can harm the eye. Besides this, some disabilities in people can slower their reflex action which might, in turn, affect the eyesight as well.