RETINAL

Retinaldehyde, better known as retinal, belongs to the vitamin A derivatives (retinoids). Retinoids increase collagen content in the upper dermis by inhibiting collagen breakdown and enhancing 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. Retinal is considered in current studies to be the most effective over-the-counter retinoid with a favorable balance of activity and tolerability. (1)

Retinal is a popular active ingredient for treating skin with signs of photoaging and is generally better tolerated than retinoic acid. Photoaging is the premature aging of the skin that occurs due to 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 general photoaging symptoms as well as a significant improvement in fine lines and skin roughness. In addition, both concentrations were able to achieve a reduction in transepidermal water loss and an increase in skin 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 occurs through keratinocytes at a specific stage of differentiation, leading to a more controlled uptake of retinoic acid. This leads to weaker 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 was able to achieve a significant increase in epidermal thickness as well as skin elasticity. The retinal treatment also led to an increase in dermal skin thickness as well as a reduction in skin stiffness and was very well tolerated by the patients. (4)

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

Overall, it can be concluded that 0.05 - 0.1% retinal is capable of reducing signs of skin aging.

Retinal has slightly 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 epidermis-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.

(2) Kwon, H. S.,Lee, J. H.,Kim, G. M.,& Bae, J. M. (2018). Efficacy and safety of etinaldehyde 0.1% and 0.05% creams used to treat photoaged skin: a randomised, double-blind, controlled trial. Journal of cosmetic dermatology, 17(3), 471–476.

(3) Mukherjee, S.,Datum, 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.

(4) Diridollou, S.,Vienna, 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 1 July 1999; 199 (Suppl. 1): 43–48.

(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.

(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.