RETINAL

Retinaldehyde, better known as retinal, belongs to the vitamin A derivatives (retinoids). Retinoids increase the collagen content in the upper dermis by inhibiting collagen degradation and increasing collagen synthesis. Retinal is a natural precursor of retinoic acid, so it only requires a single conversion step to be oxidized into the active form. In current studies, retinal is considered to be the most effective over-the-counter retinoid with a favorable ratio of activity and tolerability. (1)

Retinal is a popular active ingredient for the treatment of skin with signs of photoaging and is generally better tolerated than retinoic acid. Photoaging is the premature ageing of the skin caused by cumulative exposure to ultraviolet radiation. In a randomized double-blind study, the effect of 0.05 % and 0.1 % retinal on photoaged skin was investigated. Both concentrations were able to achieve an improvement in the general signs of photoaging as well as a significant improvement in fine wrinkles and skin roughness. In addition, both concentrations were able to achieve a reduction in transepidermal water loss and an increase in the skin's moisture content. 0.1 % Retinal was also able to achieve a significant improvement in skin pigmentation. Both concentrations were well tolerated. (2)

The metabolism of retinal to retinoic acid only takes place by keratinocytes at a certain stage of differentiation, which leads to a more controlled uptake of retinoic acid. This leads to less retinoid-related side effects such as skin irritation or redness compared to tretinoin and other retinoids, which is why retinal is generally better tolerated. (3)

In another study, 0.05% retinal significantly increased the epidermal thickness and elasticity of the skin. Retinal treatment also led to an increase in dermal skin thickness and a reduction in skin stiffness and was very well tolerated by the patients. (4)

In an ex-vivo study, significant repair of elastic fibers and collagen changes induced by UV radiation as well as increased collagen synthesis were observed. (5)

Overall, it can be concluded that 0.05 - 0.1 % retinal is able to reduce signs of skin ageing.

Retinal has mild comedolytic properties. (6) In a study on the antibacterial activity of retinal against C. acnes, the daily topical application of 0.05% retinal was also associated with a significant reduction in C. acnes density. This result indicates a direct antibacterial activity. (7)

In another study, 0.05% retinal showed the same activity profile as 0.025% retinoic acid when applied topically, namely a comedolytic and epidermal thickening effect. The results of the study support the topical application of retinal in the treatment of acne. (8)

(1) Milosheska, D. & Roškar, R. (2022). Use of Retinoids in Topical Antiaging Treatments: A Focused Review of Clinical Evidence for Conventional and Nanoformulations. Advances in therapy, 39(12), 5351-5375. https://doi.org/10.1007/s12325-022-02319-7

(2) Kwon, H. S., Lee, J. H., Kim, G. M., & Bae, J. M. (2018). Efficacy and safety of retinaldehyde 0.1% and 0.05% creams used to treat photoaged skin: A randomized double-blind controlled trial. Journal of cosmetic dermatology, 17(3), 471-476. https://doi.org/10.1111/jocd.12551

(3) Mukherjee, S., Date, A., Patravale, V., Korting, H. C., Roeder, A., & Weindl, G. (2006). Retinoids in the treatment of skin aging: an overview of clinical efficacy and safety. Clinical interventions in aging, 1(4), 327-348. https://doi.org/10.2147/ciia.2006.1.4.327

(4) Diridollou, S., Vienne, M.P., Alibert, M., Aquilina, C., Briant, A., Dahan, S., Denis, P., Launais, B., Turlier, V., & Dupuy, P. (1999). Efficacy of Topical 0.05% Retinaldehyde in Skin Aging by Ultrasound and Rheological Techniques. Dermatology, 199, 37 - 41.

(5) S. Boisnic, M.-C. Branchet-Gumila, Y. Le Charpentier, C. Segard; Repair of UVA-Induced Elastic Fiber and Collagen Damage by 0.05% Retinaldehyde Cream in an ex vivo Human Skin Model. Dermatology July 1, 1999; 199 (Suppl. 1): 43–48. https://doi.org/10.1159/000051378

(6) Zouboulis, C. C., Katsambas, A. D., & Kligman, A. M. (Eds.). (2014). Pathogenesis and treatment of acne and rosacea (pp. 121-122). Heidelberg, Germany: Springer.

(7) Péchère, M., Pechèreb, J., Siegenthalera, G., Germaniera, L., & Saurat, J. (1999). Antibacterial Activity of Retinaldehyde against Propionibacterium acnes. Dermatology, 199, 29 - 31. https://doi.org/10.1159/000051375.

(8) Fort-Lacoste, L., Verscheure, Y., Tisne-Versailles, J., & Navarro, R. (1999). Comedolytic effect of topical retinaldehyde in the rhino mouse model. Dermatology (Basel, Switzerland), 199 Suppl 1, 33-35. https://doi.org/10.1159/000051376