Abstract: The present invention provides methods of treating humans and animals with terpenes and terpenoids in order to rejuvenate the skin and increase the protective layer against irradiation by ultraviolet radiation (UVR). More specifically it provides terpenes and terpenoids as ingredients that work as persistent UVR blockers. Terpenes and terpenoid compounds support the growth of skin, skin tissue and keratinocytes and additional UVR-blocking by reason of increased stratum corneum thickness and loricrin content. Both terpenes and terpenoids may be applied topically or orally at oral or topical concentrations from about 6 mg to about 600 mg per kilogram of body weight per day effective to stimulate growth of the skin layer and prevent damage from ultraviolet radiation (UVR).