The field of cosmeceuticals is rich with active ingredients that are touted for their ability to improve the appearance of aging skin. Among the most popular and well-researched categories are botanicals, antioxidants, retinoids, and hydroxyacids.
Botanicals represent a diverse group of ingredients derived from plants, with an increasing interest in their use in skincare and cosmetic products. Herbal extracts may offer promising therapeutic benefits for photoaging due to the presence of highly reactive molecules and compounds in stable preparations. Botanicals contain various secondary metabolites (SM) such as terpenoids, alkaloids, and phenolics, which have been chemically characterised for their biological effects. These compounds can exhibit a range of activities, including antioxidant, anti-inflammatory, and anti-microbial properties. When selecting a botanical for a cosmeceutical product, practitioners should consider scientific research and traditional medical knowledge based on ethnobotany to target specific desired beneficial effects. However, the concentration and quality of active ingredients in herbal extracts can be affected by various factors, and the delivery of therapeutic concentrations across the stratum corneum remains a challenge due to the diverse solubilities, polarities, and sizes of the numerous SM present. Formulating products with herbal ingredients requires careful consideration, and ideally, the finished product should be tested for efficacy and safety. While the incidence of dangerous adverse reactions to herbal medicines is infrequent, it is growing, with sensitive skin being a common concern. Some botanical ingredients used in cosmeceuticals may also be regulated as over-the-counter (OTC) drugs if they are claimed to be therapeutic for common skin diseases like acne or psoriasis.
Antioxidants have gained considerable popularity for their potential to protect against and treat various diseases, including cancer, and to prevent aging. While the role of oral antioxidant supplements in preventing disease or slowing aging is not definitively established, the ability of antioxidants to block free radical damage to cells has led to their widespread use in topical skincare products. Free radicals, generated by factors like UV radiation and pollution, can damage cellular components and contribute to the signs of skin aging. Topical antioxidants such as vitamin E, vitamin C, and carotenoids are commonly incorporated into formulations to neutralise these free radicals in the skin. Some studies suggest that topical antioxidant mixtures containing ingredients like vitamin C and phloretin can offer protective effects against ultraviolet-induced photodamage in human skin. The question of whether or not the antioxidants in topical skin care products provide tangible skin benefits is a key area of exploration in cosmetic dermatology.
Topical cosmeceutical retinoids define a class of substances that include vitamin A (retinol) and its natural and synthetic derivatives. Retinoids are lipophilic molecules that can diffuse through plasma membranes or cross the cutaneous barrier when applied topically. Inside the cells, retinoids bind to nuclear receptors (RARs and RXRs), and the resulting ligand-receptor complexes modulate the expression of genes involved in cellular differentiation and proliferation. Retinoids are well-recognised for their ability to improve various signs of skin aging, including reducing fine lines and wrinkles, improving skin texture and tone, and addressing hyperpigmentation. Different forms of vitamin A are used cosmetically, with retinol, retinyl esters (e.g., retinyl palmitate), and retinaldehyde being the most common. These forms are converted endogenously to trans-retinoic acid, the active form of vitamin A in the skin. The use of topical retinoids is a cornerstone in the treatment of photoaging.
Clinical uses of hydroxyacids (HAs) encompass alpha-hydroxy acids (AHAs), beta-hydroxy acids (BHAs), poly-hydroxy acids (PHAs), and bionic acids. These ingredients have emerged as important technologies in the quest to reverse the clinical signs of aging and improve overall skin health due to their eudermatrophic effects, meaning they help to nourish the skin towards normalcy. HAs exert their effects primarily by modulating the stratum corneum, influencing its formation and promoting exfoliation. This process helps to improve skin texture, reduce the appearance of fine lines, and can also address dyspigmentation and skin laxity. Many HAs also provide significant protective benefits, including antioxidant, MMP-inhibition, barrier repair, and anti-glycation effects. AHAs like glycolic and lactic acid are well-known for their exfoliating properties, while BHAs such as salicylic acid are lipophilic and can penetrate pores, making them beneficial for acne-prone skin. PHAs and bionic acids offer similar benefits but are generally considered less irritating, making them suitable for sensitive skin. Hydroxyacids continue to be a mainstay in dermatology due to their efficacy and relative safety, even with long-term use. In conclusion, botanicals, antioxidants, retinoids, and hydroxyacids represent key categories of active ingredients frequently found in cosmeceutical products aimed at improving the appearance of aging skin. Each category encompasses a variety of specific compounds with distinct mechanisms of action and potential benefits, contributing to the multifaceted approach of modern cosmetic dermatology.