INTRODUCTION
Patients are increasingly looking to natural ingredients to improve the appearance of their skin and delay the effects of aging. The aging process in the skin is due to a combination of intrinsic and extrinsic factors, among which ultraviolet (UV) radiation is believed to play an important role. UV radiation facilitates aging by increasing reactive oxidation species and cellular damage, epidermal hypertrophy, hyperpigmentation, degradation of extracellular matrix proteins and dermal collagen, and producing phototoxic effects such as erythema, edema, and inflammation.1,2,3,4 Skin care products promise anti-aging effects by counteracting these various factors.Many of these natural anti-aging ingredients are emerging from Asian countries like South Korea, one of the world’s most innovative and fastest growing beauty markets. Although South Korea has a population of 50 million compared to the U.S. population of 300 million, the South Korea skin care market is worth $4.4 billion, rivaling the U.S. skin care market at $5 billion.5 South Korean skin care products focus on anti-aging and skin whitening using natural botanical and animal ingredients such as green tea, ginseng, and snail serum. As these products permeate the US market, patients are turning to dermatologists for advice on their efficacy, emphasizing the need for a critical understanding of the underlying evidence.
METHODS
We evaluated the scientific literature for the efficacy of nine natural active ingredients in the top selling brands emerging from the South Korean cosmeceutical industry. Available industrial profit data was obtained from Euromonitor to identify the top cosmeceutical brands by retail market value in South Korea (Figure 1). The top-selling products of these brands were then discovered on the brand websites, and a list of the products’ active ingredients was compiled (Table 1). The nine active ingredients were chosen based on frequency listed and availability of literature on PubMed. In vitro, preclinical in vivo, and clinical studies of the topical application of these active ingredients were identified, and the best available evidence was critically evaluated and is presented here within (Table 2). Exclusion criteria included other applications (ie, oral) of these ingredients and popular ingredients with no available scientific studies at the time this paper was written.LicoriceLicorice extract, also known as Glycyrrhiza uralensis, is derived from the root of the Glycyrrhiza glabra plant, a legume native to Europe and Asia.Licorice is frequently utilized in South Korean skin care products for its anti-inflammatory effects. Licochalcone A (LicA), an active ingredient in licorice extract, was shown in vitro to decrease prostaglandin E2, leukotriene B4, interleukin-6, and tumor necrosis factor- alpha in human keratinocytes.6 In a randomized, controlled clinical study, irritated skin treated with 0.025% of LicA-rich licorice extract was found to be less erythematous compared to vehicle alone by spectrophotometry.6 LicA may also effectively reduce sunburn erythema. Patients treated with 0.05% of the LicA-rich licorice extract and vehicle immediately and 5 hours after exposure to UVB irradiation had significantly less erythema where the LicA was applied. The erythema-reducing ability of LicA was also evaluated in patients with mild to moderate rosacea using 4 different types
