Compendium of the most significant studies with reference to properties, intake, effects.

Juncan AM, Moisă DG, Santini A, Morgovan C, Rus LL, Vonica-Țincu AL, Loghin F. Advantages of Hyaluronic Acid and Its Combination with Other Bioactive Ingredients in Cosmeceuticals. Molecules. 2021 Jul 22;26(15):4429. doi: 10.3390/molecules26154429. 

Abstract. This study proposes a review on hyaluronic acid (HA) known as hyaluronan or hyaluronate and its derivates and their application in cosmetic formulations. HA is a glycosaminoglycan constituted from two disaccharides (N-acetylglucosamine and D-glucuronic acid), isolated initially from the vitreous humour of the eye, and subsequently discovered in different tissues or fluids (especially in the articular cartilage and the synovial fluid). It is ubiquitous in vertebrates, including humans, and it is involved in diverse biological processes, such as cell differentiation, embryological development, inflammation, wound healing, etc. HA has many qualities that recommend it over other substances used in skin regeneration, with moisturizing and anti-ageing effects. HA molecular weight influences its penetration into the skin and its biological activity. Considering that, nowadays, hyaluronic acid has a wide use and a multitude of applications (in ophthalmology, arthrology, pneumology, rhinology, aesthetic medicine, oncology, nutrition, and cosmetics), the present study describes the main aspects related to its use in cosmetology. The biological effect of HA on the skin level and its potential adverse effects are discussed. Some available cosmetic products containing HA have been identified from the brand portfolio of most known manufacturers and their composition was evaluated. Further, additional biological effects due to the other active ingredients (plant extracts, vitamins, amino acids, peptides, proteins, saccharides, probiotics, etc.) are presented, as well as a description of their possible toxic effects.

Purnamawati S, Indrastuti N, Danarti R, Saefudin T. The Role of Moisturizers in Addressing Various Kinds of Dermatitis: A Review. Clin Med Res. 2017 Dec;15(3-4):75-87. doi: 10.3121/cmr.2017.1363.

Abstract. Moisturizer is a major component of basic daily skin care, particularly in presence of epidermal barrier alteration and reduced epidermal water content. It is an important part of a dermatologist's strategy to maintain skin health as well as treating various dermatoses which co-exist with skin dryness and are linked to impaired skin barrier function, such as in atopic disorders as well as other types of dermatitis. Mastering the knowledge regarding mechanism of action, application, dosage, adverse effects as well as specific clinical usage of moisturizers is a must for a dermatologist in order to support their use, particularly for evidence-based, therapeutic purposes. This review discusses the use of moisturizer both for skin health maintenance as well as a definitive or adjuvant therapy for many kinds of dermatitis. © 2017 Marshfield Clinic.

Kanlayavattanakul M, Lourith N. Lipopeptides in cosmetics. Int J Cosmet Sci. 2010 Feb;32(1):1-8. doi: 10.1111/j.1468-2494.2009.00543.x. 

Abstract. Lipopeptides are biosurfactants extensively used in cosmetics. The consumption of cosmetics containing lipopeptides is increasing as a result of the exceptional surface properties and diverse biological activities of lipopeptides which facilitate a vast number of applications not only in the pharmaceutics industry which includes cosmetics but also in the food industry. Cosmetics containing lipopeptides are available in various dosage forms according to their beneficial surface properties, which include anti-wrinkle and moisturizing activities and cleansing cosmetics. The microbial production of lipopeptides particularly those with biological and surface activities applicable to cosmetics are summarized based on appropriate studies and patents up to the year 2008 to manage the information and sufficiently review the data.

Goodman G. Cleansing and moisturizing in acne patients. Am J Clin Dermatol. 2009;10 Suppl 1:1-6. doi: 10.2165/0128071-200910001-00001. 

Abstract. Affecting over 80% of adolescents, acne is a widespread condition with substantial negative physical and emotional effects, and significant societal cost. Cleansing the acne patient involves several considerations, including matching skin type to the right type of cleanser, optimal times and methods of cleansing, treating parts of the body other than the face, and patient perceptions of the cause and treatment of acne. Moisturizing prevents and alleviates skin irritation, soothing the skin by slowing the evaporation of water. Many liquid face cleansers also moisturize, which may be all that is needed for a patient with oily skin. Protection from sun and environmental damage is important for all patients. While sunscreens are often irritants, the best options for young, oily, acne-prone skin tend to have a water or light liquid base. Moisturizing sunscreens are appropriate for patients with dry, sun-damaged skin, as well as those who wear makeup, have other skin diseases, or are easily irritated by products. Overall, treating acne patients should include education in patient-friendly terms and promoting healthy daily skin care practices, including cleansing and protection against environmental damage.

Morita T, Fukuoka T, Imura T, Kitamoto D. Production of mannosylerythritol lipids and their application in cosmetics. Appl Microbiol Biotechnol. 2013 Jun;97(11):4691-700. doi: 10.1007/s00253-013-4858-1. 

Abstract. Mannosylerythritol lipids (MELs) are glycolipid biosurfactants abundantly produced by different basidiomycetous yeasts such as Pseudozyma, and show not only excellent interfacial properties but also versatile biochemical actions. These features of MELs make their application in new technology areas possible. Recently, the structural and functional variety of MELs was considerably expanded by advanced microbial screening methods. Different types of MELs bearing different hydrophilic and hydrophobic parts have been reported. The genes responsible for MEL biosynthesis were identified, and their genetic study is now in progress, aiming to control the chemical structure. The excellent properties leading to practical cosmetic ingredients, i.e., moisturization of dry skin, repair of damaged hair, activation of fibroblast and papilla cells and antioxidant and protective effects in skin cells, have been demonstrated on the yeast glycolipid biosurfactants. In this review, the current status of research and development on MELs, particularly the commercial application in cosmetics, is described.

Madison KC. Barrier function of the skin: "la raison d'être" of the epidermis. J Invest Dermatol. 2003 Aug;121(2):231-41. doi: 10.1046/j.1523-1747.2003.12359.x. 

Abstract. The primary function of the epidermis is to produce the protective, semi-permeable stratum corneum that permits terrestrial life. The barrier function of the stratum corneum is provided by patterned lipid lamellae localized to the extracellular spaces between corneocytes. Anucleate corneocytes contain keratin filaments bound to a peripheral cornified envelope composed of cross-linked proteins. The many layers of these specialized cells in the stratum corneum provide a tough and resilient framework for the intercellular lipid lamellae. The lamellae are derived from disk-like lipid membranes extruded from lamellar granules into the intercellular spaces of the upper granular layer. Lysosomal and other enzymes present in the extracellular compartment are responsible for the lipid remodeling required to generate the barrier lamellae as well as for the reactions that result in desquamation. Lamellar granules likely originate from the Golgi apparatus and are currently thought to be elements of the tubulo-vesicular trans-Golgi network. The regulation of barrier lipid synthesis has been studied in a variety of models, with induction of several enzymes demonstrated during fetal development and keratinocyte differentiation, but an understanding of this process at the molecular genetic level awaits further study. Certain genetic defects in lipid metabolism or in the protein components of the stratum corneum produce scaly or ichthyotic skin with abnormal barrier lipid structure and function. The inflammatory skin diseases psoriasis and atopic dermatitis also show decreased barrier function, but the underlying mechanisms remain under investigation. Topically applied "moisturizers" work by acting as humectants or by providing an artificial barrier to trans-epidermal water loss; current work has focused on developing a more physiologic mix of lipids for topical application to skin. Recent studies in genetically engineered mice have suggested an unexpected role for tight junctions in epidermal barrier function and further developments in this area are expected. Ultimately, more sophisticated understanding of epidermal barrier function will lead to more rational therapy of a host of skin conditions in which the barrier is impaired.

Draelos ZD, Gunt H, Zeichner J, Levy S. Clinical Evaluation of a Nature-Based Bakuchiol Anti-Aging Moisturizer for Sensitive Skin. J Drugs Dermatol. 2020 Dec 1;19(12):1181-1183. doi: 10.36849/JDD.2020.5522.

Abstract. Background: Patients with sensitive skin find topical retinoid use for anti-aging purposes challenging due to irritation. Bakuchiol, a meroterpene from the Psoralea corylifolia seed, has retinol functionality through retinol-like regulation of gene expression. Objective: This research examined the tolerability, efficacy, and barrier effects of a nature-based bakuchiol-containing cleanser and moisturizer in subjects with sensitive skin....Conclusion: A bakuchiol nature-based anti-aging moisturizer is well tolerated and effective in individuals with sensitive skin.

Lourenco EAJ, Shaw L, Pratt H, Duffy GL, Czanner G, Zheng Y, Hamill KJ, McCormick AG. Application of SPF moisturisers is inferior to sunscreens in coverage of facial and eyelid regions. PLoS One. 2019 Apr 3;14(4):e0212548. doi: 10.1371/journal.pone.0212548. 

Abstract. Many moisturisers contain sun protection factors (SPF) equivalent to those found in sunscreens. However, there is a lack of research into how SPF moisturiser application compares to sunscreens in terms of coverage achieved and protection afforded. Previously we demonstrated that users incompletely covered their eyelid regions during routine sunscreen application. Here, we aimed to determine if SPF moisturiser users also displayed these tendencies. A study population of 84 participants (22 males, 62 females, age 18-57) were exposed to UV radiation and photographed using a tripod mounted UV sensitive DSLR camera on two separate visits. At visit one, images were acquired before and after applying either SPF30 sunscreen or moisturiser, then at visit two the study was repeated with the other formulation. Images were processed for facial landmark identification followed by segmentation mapping of hue saturation values to identify areas of the face that were/were not covered. Analyses revealed that application of moisturiser was significantly worse than sunscreen in terms area of the whole face missed (11.1% missed with sunscreen compared to 16.6% for SPF moisturiser p<0.001 paired t-test). This difference was primarily due to decreased coverage of the eyelid regions (14.0% missed with sunscreen, 20.9% moisturiser, p<0.001). Analysis of a post-study questionnaire revealed participants to be unaware of their incomplete coverage. Secondary analyses revealed improved coverage in males (p = 0.05), and, with moisturiser only, in participants with darker skin tones (p = 0.02). Together these data indicate that, despite potential advantages in terms of increased frequency of application of moisturiser, the areas of the face that are at higher cancer risk are likely not being protected, and that participants are unaware that they are at risk. As such, alternative sun-protection strategies should be promoted.