71 NATURAL ACTIVE INGREDIENTS AND SKIN HYDRATION found that TEWL values increased after the use of formulation with cucumber extracts. They caused disruption of the skin, thus increasing the rate of water evaporation from the SC and leading to reduction of skin moisture. However, these effects were statistically insignificant (p 0.05) (25). In addition, studies of C asiatica have shown effectiveness in skin hydration that has resulted from improvement in elasticity and firmness of the skin (14). A total of 20 healthy women, with a mean age of 40 years old, were enrolled in an intrasubject (right versus left), randomized, assessor-blinded, controlled, 1-day trial. The primary end points were the skin hydration and TEWL, evaluated at the volar surface of the forearm and in standardized conditions (temperature- and humidity-controlled room: 23°C and 30% of humidity). The author found that a single application of the fluid containing C asiatica extract, HA, and glycerin, significantly improved skin hydration for up to 24 hours while improving skin barrier function. In addition, a study by Vaughn et al. (15) stated that almond oil is rich in vitamin E and has been shown to have occlusive properties, thus improving skin hydration. The author conducted a multicenter randomized, clinical study of the effects of natural oils on xerosis and skin barrier properties. The study outcome showed that almond oil, jojoba oil, and coconut oil significantly increased hydration after 2 weeks and are as effective as white petrolatum as daily moisturizers for xerosis. The participants also preferred natural oils over white petrolatum, which indicates that these moisturizer options may improve patient compliance. EMOLLIENTS AND HUMECTANTS IN COSMETIC FORMULATIONS ON SKIN CONDITION The emollient action of some ingredients is a consequence of skin softening, smoothing, and moisturizing capacity (26). These compounds have the ability to maintain almost 25% of the water in corneocytes and protect the skin barrier (27,28). The main functions of emollients are to protect and help maintain skin sebum and lipid levels (28). The topical application of these compounds improves skin hydration and prevents the appearance of dry skin (29). In physiological terms, emollients create a thin layer on the skin’s surface that is able to prevent water evaporation (28). Compounds such as ceramide, cholesterol, and free fatty acid may be included in cosmetic and medical skin-care formulations to improve barrier homeostasis and, consequently, hydration and sebum levels (30). Palm oil is a natural oil that has emollient properties and does not create any irritation effects on the skin (31). In addition, palm oil has moisturizing properties by reducing the level of dryness and roughness of skin. It works by strengthening the water-binding capacity of the SC (11). According to Fluhr et al., palm oil works by forming an occlusive film that inhibits water evaporation from beneath the skin. Palm oil contains tocotrienols, with the highest levels among all vegetable oils, and tocopherols (32,33) Shea butter also exhibits emollient properties, protecting the skin by stimulating the production of structural proteins by specialized skin cells (10). A study by Nandal et al. (34) found that aloe vera is useful for maintaining skin moisture and helping to sooth the skin to prevent dryness due to harsh weather. Aloe vera can also be used as a moisturizer for oily skin. It acts by improving the skin’s ability to hydrate itself, helps in removal of dead keratin cells, and has an effective penetrating ability that aids in transporting healthy materials through the skin barrier (34). Development of aloe sugar with a combination of selected essential oils makes it an excellent moisturizing agent that helps to smoothen the skin. A study by Sajjad et al. (35) stated that aloe vera extracts act

72 JOURNAL OF COSMETIC SCIENCE as humectants they attract water from the deeper parts of skin and help keep the water bound in the SC. The humectant mechanism of aloe vera improves skin hydration. These factors make aloe vera an ideal ingredient in cosmetic and dermatological products. A study by Vaughn et al. (36) stated that argan oil was found to have good emollient properties and was effective in reducing dryness of skin thus, it helped to enhance the skin condition. Almond oil contains highly active natural humectants and emollients, which possess excellent moisturizing abilities, to prevent the skin from drying out, thus avoiding peeling or chapping. Almond oil has properties that nourish, sooth, protect, and calm the skin by helping the epidermis maintain optimum moisture levels (37–39). Jin et al. (40) evaluated the nutritional composition of Actinidia arguta (kiwi berry), reporting the presence of palmitic acid (a saturated fatty acid) and α-linoleic acid (an unsaturated fatty acid). Fatty acids—such as lauric acid, linoleic acid, palmitic acid, stearic acid, linolenic acid, myristic acid, oleic acid, and isostearic acid—are known as skin penetration enhancers in topical and transdermal formulations (41). Linoleic and α-linoleic acids have influence on the skin physiology and can be oxidized to eicosanoids, which are extremely important compounds in cell signaling (42). Similarly, linoleic acid is described as a topical treatment for skin inflammation (43). Fluhr et al. (44) applied free fatty acids—such as palmitic acid, stearic acid, and linoleic acid in murine skin surfaces—concluding that they play an important role in acidification, integrity, and cohesion of the SC. In addition, topical application of polyunsaturated fatty acid was shown to induce the hyperproliferation in guinea pig skin (45). Furthermore, fatty acids are easily incorporated in cell membrane lipids, improving the epidermis lipid barrier and softening the SC (26). Barcelos et al. (46) administered daily omega-3 fish oils (FOs) to rats and observed the changes in dermal responses to skin irritation after 30, 60, and 90 days of supplementation. After 60 days of supplementation, both irritation and TEWL were significantly reduced in response to acetone exposure. After 90 days, TEWL had gone down by 50% compared with the control group without FO. Cutaneous hydration significantly increased by 30% after 60 days of FO treatment, which was maintained after 90 days compared with the control group. This supports previous claims that dietary fatty acids are transported to the SC (47,48) and are able to improve cutaneous health through oral administration. MARINE SOURCES IN COSMETIC FORMULATIONS AND SKIN HYDRATION The expanding market and increasing demand for skin-care products and continual studies on new ingredients in cosmetic formulations have led to a revolution in cosmetic products based on marine constituents (49). According to a study by Silvipriya et al., marine sources were found to be the safest sources of collagen. Collagen is the major structural protein constituting the extracellular matrix of connective tissues and is widely used in various industries such as medical tissue regeneration (50), pharmaceuticals, food, and cosmetics. Collagen is biocompatible and biodegradable, which enables superior cell accommodation with a relatively low immunogenicity compared with other biomaterials (51). Hydrolyzed collagens, or small-molecular-weight peptides, have been found to penetrate deep layers of the skin easily compared with high-molecular weight native collagens. They play an important role in fibroblast growth (52), collagen expression (53), and strong collagen fiber formation in the epidermis (54). In addition, they are important molecular components in improving the functionality of the skin layer by increasing the water content of the SC (55).