Sunlight is the main environmental factor influencing human skin. The sun-light’s terrestrial spectrum is different from the extraterrestrial one, sunlight being changed by the filter effect of ozone and particles in the stratosphere and atmosphere. Attention is drawn to the influence of ‘supersonic transporters’ (SST) and chlorofluoromethanes on this protective ozone shield. The cascade of events which occur in human skin after sun exposure are schematically listed. The mechanisms of protection and the processes of adaptation including their respective values are presented. An overexposure induces acute clinical symptoms and leads, as a late effect, to potential malignancies.