Rosehip seed oil is an excellent source of natural vitamin E and natural vitamin A, or 'trans-retinoic acid'. Retinoic acid, the acid derivative of vitamin A, is the active ingredient found in Retin-A or Tretinoin. Retin-A (a pharmaceutical preparation) has been heralded as a wrinkle cure because of its ability to increase skin cell proliferation - or speed the time it takes for your skin to regenerate. In fact, rosehip seed oil has been extensively studied for many of the same actions attributed to Retin-A, and has been shown effective without side effects (like over-drying and peeling - though unlike Retin-A, it should not be used to treat acne).
The first major study on rosehip seed oil was performed in 1983 by a team of researchers at the University of Santiago, Chile. The study's participants included individuals with diverse forms of skin damage: deep wrinkles and other premature aging, UV damage, radiation damage, acne scarring, burn scarring, dermatitis, and other problems of this type. Rosehip seed oil was shown to have significant, noticeable effects in regenerating the skin, reducing wrinkles and scars, and helping the skin to regain its natural color and tone.
RoseHip - http://www.aromatherapy-blends.net/rosehip-aromatherapy.htm