## 4 Components of Emollients and Their Effect on the Changes That Occur in Atopic Dermatitis
Lanolin and its derivatives are among the components of emollients that permanently restore the epidermal barrier, as its effects are longer lasting than those of occlusive emollients [1]. The authors point out that lanolin contained in cosmetics replenishes lipids in the stratum corneum reducing dryness of the skin, protects the skin from drying and cracking [52]. Lanolin is structurally similar to the structure of fetal synovial lipids, which is beneficial for restoring the epidermal barrier among newborns [1]. Until recently, lanolin was a common cause of allergy by the presence of fractions of free lanolin alcohols [1]. The above claims are explained by the concept of the lanolin paradox presented in 1986 by [PERSON], who pointed out that lanolin is a component of drugs responsible for sensitization in a large number of patients, but at the same time is a safe compound in the general population [87]. According to the authors of [1], non-allergeric lanolin derivatives (liquid lanolin, as well as acetylated and ethovylated lanolin alcohols) are currently in use. Confirmation of the validity of the introduction of natural ingredients into the preparations used in the care of atopic skin was the work conducted by the authors [88; 89; 90; 91]. The aforementioned authors confirmed the significant role of fats and oils in moisturizing the skin, specifically sheep tallow, hemp oil and walnut oil, while taking into account the benefit of introducing enzyme-modified fats into therapeutic preparations. They indicated that the model formulations they obtained may be used as moisturizing formulations and also as a preparation in the treatment of dry skin. One of the commonly used ingredients of animal origin in emollients is honey [85; 92]. Honey is a substance that deeply nourishes the epidermis and is rich in enzymes that naturally exfoliate the skin [85]. It is usually added to the formulation of cosmetics used at night and recommended for dry or mature skin [92]. Honey has humectant properties due to its high glucose and fructose content. Both of these substances can form hydrogen bridges with water [92]. According to the above authors, this increases water retention in the stratum corneum of the skin, which consequently increases hydration. Studies emphasize that honey's moisturizing effect is also due to the presence of amino acids (proline, arginine, alanine, lysine, glycine, among others) and organic acids (gluconic acid, lactic acid, citric acid, succinic acid or acetic acid), which have corresponding functional groups (such as amine or carboxyl) [93]. They can form hydrogen bonds, enhancing the effect of water retention in the stratum corneum of the skin. According to the authors of [92; 93], honey exerts a pH-regulating effect and prevents infections, due to its antimicrobial properties. Three factors contribute to this: the osmotic effect (allowing honey to interact strongly with water, leaving insufficient water for microorganisms), the acidic pH of honey and the release of hydrogen peroxide by the enzyme glucose oxidase. One of the components of emollients is also ceramides, which, delivered in appropriate concentrations and proportions, improve the skin barrier and moisturize the skin [24; 59]. They maintain the integrity of the skin barrier, which helps prevent water loss [24; 59]. Studies have shown that the skin of patients with atopic dermatitis usually has reduced levels of ceramides [59]. However, in most cases, the ceramide content of over-the-counter remedies is too low to provide the above effects. When ceramides are provided without the addition of two other key lipids (cholesterol and at least one fatty acid), the epidermal barrier deteriorates [53]. Studies have confirmed that in order to restore normal skin barrier function, these three components should be supplied in a specific ratio [53]. One randomized study involving 100 patients divided into two groups evaluated the efficacy of a cream that contained ceramides and magnesium in the treatment of mild to moderate atopic dermatitis [94].