Oxidative stress (UV irradiation, free radicals) plays a significant role in aging. Coenzyme Q10 (CoQ10) and exogenously applied antioxidants can significantly reduce the formation of oxidative stress with increasing age. In our in vitro and in vivo experiments concerning the parameters of ultraweak photon emission (UPE), intracellular thiol status, mitochondrial membrane potential and cell vitality, we demonstrated a diminished resistance in keratinocytes of old donors against UV irradiation. This reduced epidermal resistance against oxidative stressors, i.e. UV irradiation, can be improved by topical application of CoQ10 and antioxidants like alpha-glucosylrutin (15). Furthermore, our in vivo investigations show that wrinkles around the region of the eyes ("crow feet") could be reduced by long-term application of CoQ10.