The role of vitamin A in skin regeneration In 1962 all-trans retinoic acid (tretinoin) was used to clinicaly treat ichthyoses, a condition that results in persistantly thick, dry, fishtail like skin.  Tretinoin was shown to affect keratinisation, where cells lose their moisture and are replaced by horny cells.

In 1969 further studies showed how it was effective in the treatment of acne.

In 1970 it was approved as a prescription only medication for the treatment of mild to moderate acne.

In 1986 a short term study showed that retinol normalised the keratinization in photoaged skin, with significant enhancements in the appearance of the epidermis but minimal changed to the dermis.  Longer term studies, of 6 months, showed significant improvements in fine and coarse wrinkles, sallowness, hyperpigmentation and roughness.  Studies lasting 12 months or more showed clinical changes in the dermis, with new collagen production, and regulation of the damaged tissue. There were unfortunately downsides to tretinoin; increased erythema, inflammation and photosensitisation.

In 1984 retinol was available for use as a cosmetic ingredient for its use in ageing and photodamaged skin amd was generally regarded as safe.  Skin tolerance to retinol had been shown to be significantly greater than tretinoin, with similar results.  A study in 2013 showed improved visible signs of photodamage after 8 and 12 week of daily use.   Hyper pigmentation, skin laxity, roughness and actinic keratosis showed significant improvement after 4 and 8 weeks of daily use.

Topical vitamin A plays a key role in the treatment of aged skin and photodamaged skin, providing visible and physical enhancement, with effects seen after just 4 weeks of daily use.  The greatest physiological effects seen after daily use of 12 months or more, ensuring that retinol based products will continue to play a significant role in the clinical management of aged and photodamaged skin.

Medik8 provide retinol serums in 4 different strengths, from 0.1% to 0.10% to treat all skin types and conditions.

references -  Aesthetics journal.