INTRODUCTION
Retinoids are derivatives of Vitamin A used to treat myriad dermatological conditions including acne, psoriasis, and skin cancer. They are also prominently used in skincare as an "anti-aging" treatment in various concentrations and forms. All-trans retinoic acid, commonly known as tretinoin, is available by prescription and is the most widely investigated retinoid for photoaging. All-trans retinoic acid regulates over 3000 genes in keratinocytes and fibroblasts, and when these receptors are activated, it can increase cell turnover and motility, increase synthesis of procollagen and glycosaminoglycans, and inhibit matrix metalloproteinases.1,2 Retinoic acid precursors including retinyl esters, retinol, and retinaldehyde (aka retinal) are available over the counter. These precursors require enzymatic conversion in the skin prior to becoming retinoic acid, the bioactive form, and thus are considered less potent but also less irritating than retinoic acid. The potency of the retinoid inversely correlates with the number of in vivo chemical conversions necessary to create all-trans retinoic acid. Retinal specifically has been gaining traction in the skincare industry for being the most potent retinoid available without a prescription.
As we age, the skin loses its proliferative capacity and becomes thinner, drier, and less elastic. The use of retinoids has been shown to increase epidermal proliferation and increase the deposition of glycosaminoglycans, essentially reversing these signs of aging. All-trans retinoic acid has been studied extensively for its ability to drive measurable clinical improvements in photoaging and overall appearance of the skin after several months of consistent use. Though tretinoin is the strongest retinoid, it can cause significant erythema, irritation, burning, or dermatitis, often causing patients to discontinue use.2 The most dramatic benefits in terms of photoaging are often appreciated after 6 months of consistent use, and consequently, there is great demand for retinoids that are effective but better tolerated.2 Retinol requires 2 conversion steps to become retinoic acid and is considered 20 times less potent than tretinoin.
Nonetheless, retinol has been shown to improve signs of photoaging with less transepidermal water loss, erythema, and scaling of the skin than tretinoin.2 Retinal, on the other hand, only requires 1 conversion step to become retinoic acid, making it the strongest over-the-counter retinoid.3 Retinal has been
