![]() The mechanism of action is as shown in Figure 1. Trihydroxylated molecule glycerol is the most effective humectant. Table 3 lists the various humectants available. Natural moisturizing factor made of a mixture of low molecular weight soluble hygroscopic substances such as lactic acid, pyrrolidone carboxylic acid, and amino acids is a major player for hydration of the SC. Many humectants have emollient properties as well. They are basically hygroscopic compounds which mean they attract water from two sources, from the dermis into the epidermis and in humid conditions from the environment. Various types of emollients are as shown in Table 2. Besides its emollient action, it is also used in treating skin disorders such as seborrheic dermatitis, acne, psoriasis, or atopic dermatitis. Squalane is thus more commonly used as a moisturizer.Īn added boon of squalane is that even though it is technically oil, it does not have an oily feel, is odorless, noncomedonal, antibacterial, and is safe for sensitive skin. Squalane is less susceptible to oxidation than squalene. Squalane is a saturated form of squalene in which the double bonds have been eliminated by hydrogenation. It acts as a quencher of singlet oxygen, protecting human skin surface from lipid peroxidation due to exposure to ultraviolet (UV), and other sources of ionizing radiation. It can be derived from both plant and animal sources. Although squalane is produced naturally by the body, the production of this chemical slows drastically after age thirty, thus contributing to dry skin. It is transported in serum generally in association with very low-density lipoproteins and is distributed ubiquitously in human tissues, with the greatest concentration in the skin. In humans, about 60% of dietary squalene is absorbed. It is an isoprenoid compound and acts as an intermediate metabolite in the synthesis of cholesterol. Squalene is one of the most common lipids produced by human skin cells and is a component of human sebum. Canola oil in specific is known to reduce sodium lauryl sulfate (SLS) irritation. They influence skin physiology and pathology via their effects on skin barrier functions, eicosanoid production, membrane fluidity, and cell signaling. Long chain saturated fatty acids, for example, stearic, linoleic, oleic, and lauric acid and fatty alcohols are essential fatty acids that are found naturally in palm oil, coconut oil, and wool fat. Nanoencapsulated triceramides are also being used for increasing the hydration of the skin. They get easily incorporated into liposomes and make the skin texture softer and smoother. Lipophilic compounds such as cholesterol and ceramides are being used in topical skin creams. Hence, several pseudo-ceramides are useful as emollients. Natural ceramides or the synthetic ones are too expensive. In SC, ceramides are the major lipid constituents and along with neutral lipids, they form broad laminated intercellular sheets, which act as barriers to our environment. Intracellular lipids comprising multilamellar, which are located between SC play a major role in skin architecture. The skin slip or lubricity contributes to consumer satisfaction. They are mainly lipids and oils, which hydrate and improve the skin softness, flexibility, and smoothness. Dryness is not a single entity but is characterized by differences in chemistry and morphology in the epidermis depending on the internal and external stressors. Consumers regard them to increase the water content of the skin while dermatologists consider them as bland oleaginous substances. The term “moisturizer” is a marketing term with little or no scientific meaning. The majority of the human population applies many moisturizers throughout their lifetime it thus behooves a dermatologist to have a comprehensive knowledge of the same. The incidence of dryness related dermatoses are on the increase courtesy urbanization, adulteration, pollution, increased life span, and abandonment of traditional oil massages and baths. Moisturizers are perhaps the most prescribed products in dermatology practice and also the most intriguing one. There has been a recent migration in humankind's way of thinking toward a desire for holistic products, especially pertaining to skin care.
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