Hydration skin

Human skin is the largest organ in the human body. It is fundamentally important to health as the semi-permeable barrier - the first line of defence - between the body and the external world. However, it remains relatively inaccessible to conventional magnetic resonance imaging, firstly because it is thin and therefore requires high spatial resolution, and secondly because it is characterized by relatively short T2 relaxation times, particularly in the outermost stratum comeum. Conventional studies have not usually achieved a resolution better than 70-150 pm, with an echo time of the order of a millisecond or so. As a planar sample, skin has proved amenable to GARField study where it has been possible to use both a shorter echo time and achieve a better spatial resolution, albeit in one direction only. Such studies have attracted the interest of the pharmaceutical and cosmetic industries that are interested in skin hydration and the transport of creams and lotions across the skin. 

Sebum is released by the sebaceous glands and naturally maintains hair and skin hydration. An increase in androgen levels, especially during puberty, can cause an increase in the size of the sebaceous gland and the production of abnormally high levels of sebum within those glands. This excess sebum can result in plugged follicles and acne formation. 

Humidity and temperature also affect permeability. It has long been known that skin hydration, however brought about, increases skin permeability. Occlusive... 

The extent of hydration or solvation of a molecule also has a profound effect on the transport of the substance. The apparent solubility of the drug in both aqueous and nonaqueous media may be influenced by the absence or presence of moisture. Diffusion of drugs in polymeric systems may also be influenced by the hydration of the polymers and hydration of the membrane through which transport is occurring for example, skin hydration may enhance the diffusion of drug molecules significantly. 

Nonloaded and loaded SLN were already investigated with respect to use in cosmetics. Although adequate controls are difficult to prepare, first experiments indicate an increase in skin hydration and a reduction in wrinkle depth following SLN application [68]. Moreover, cetyl palmitate-nanodispersions act both as particulate ultraviolet (UV) blockers themselves and as carriers for UV absorbing agents (e.g., 2-hydroxy-4-methoxy benzophenone Eusolex 4360). This results in a threefold... 

Wissing, S. A. and Muller, R. H., The influence of solid hpid nanoparticles on skin hydration and viscoelasticity in vivo study. Eur. J. Pharm. Biopharm., 56, 67-72, 2003. 

Mecfianism of Action A mineral that acts as a cofactor for enzymes that are important for protein and carbohydrate metabolism. Therapeutic Effect Zinc oxide acts as a mild astringent and skin protectant. Zinc sulfate helps maintain normal growth and tissue repair as well as skin hydration. 

Squalene is a polyunsaturated hydrocarbon with a formula of C30H50 Squalene can be found in certain fish oils, especially shark liver oil, in high amounts and some vegetable oils in relatively smaller amounts. Human sebum also contains 13% squalene as one of its major constituents. Squalane is a saturated derivative of squalene and also found in these sources. Interest in squalene has been raised after its characterization in shark liver oil which is used as a traditional medicine for decades. Several studies exhibited results that prove certain bioactivities for squalene and squalane. Up to date, anticancer, antioxidant, drug carrier, detoxifier, skin hydrating, and emollient activities of these substances have been... 

As an emollient, squalene is expected to increase skin hydration due to skin surface occlusions. In addition, squalene is a substance believed to maintain moisture in the stratum corneum. Novel substitutes were researched for vernix caseosa which is a reported highly efficient barrier cream for facilitating stratum corneum hydration for barrier-deficient skins. For this purpose, various lipid fractions were mixed with squalene, triglycerides, cholesterol, ceramides, and fatty acids to produce a mixture that can generate similar compositions of vernix caseosa (Rissmann et ah,... 

Bond, J.R., and B.W. Barry. 1986. Limitations of hairless mouse skin as a model for in vitro permeation studies through human skin Hydration damage. J Invest Dermatol 90 486. 

El Maghraby, G.M., A.C. Williams, and B.W. Barry. 2001. Skin hydration and possible shunt route penetration in controlled estradiol delivery from ultradeformable and standard liposomes. J Pharm Pharmacol 53 1311. 

In a related study [62], in vivo skin hydration was monitored by FUR after occlusive application of either NAT 106 liposomes prepared in D20 or pure D20. Liposomes were superior, compared with pure D20, in driving D20 into the skin, and the phospholipid components could be detected in deeper SC layers. The presence of phospholipids deep in the SC confirmed the results observed with freeze fracture, in which strong interactions between phospholipid layers and SC were observed. 

H. E. Bodde, L. A. R. M. Pechtold, M. T. A. Subnel, and F. H. N. de Haan, Monitoring in vivo skin hydration by liposomes using infrared spectroscopy in conjunction with tape stripping, Liposome Dermatics (O. Braun Falco, H. C. Korting, eds.), Springer Verlag 1992, pp. 137-149. 

Proksch, E. Nissen, H-P. Bremgartner, M. Urquhart, C., Bathing in a magnesium-rich Dead Sea salt solution improves skin barrier function, enhances skin hydration, and reduces inflammation in atopic dry skin. Int. J. Dermatol. 44, 151-157, 2005. 

Seasonal changes affect the condition of normal skin and may trigger various cutaneous disorders.28,29 In common dermatitis, a decline in barrier function often parallels the increased severity of clinical symptomatology. All these conditions tend to worsen during the winter season when humidity is low.30,31 Abundant indirect evidence indicates that decreased humidity precipitates these disorders, whereas, in contrast, increased skin hydration appears to ameliorate these conditions. The mechanisms by which alterations in relative humidity might influence cutaneous function and induce cutaneous pathology are poorly understood. 

Hara, M. and Verkman, A.S., Glycerol replacement corrects defective skin hydration, elasticity, and barrie function in aquaporin-3-deficient mice, Proc. Natl. Acad. Sci. USA, 100, 7360-7365, 2003. 

Despite the well-known clinical coupling of dry skin and itch, studies to objectively compare the degree of skin hydration or measurements of the transepidermal water losses with severity of pruritus have provided conflicting results on this close association. This review will discuss the existing data, breakdown the pathophysiology of xerotic itch, and describe the role of moisturizers in alleviating both entities. 

Held, E., Sveinsdottir, S., and Agner, T. Effect of long-term use of moisturizers on skin hydration, barrier function and susceptibillity to irritants. Acta. Derm. Venerol. 1999 79 49-51. 

Loden, M. The increase in skin hydration after application of emollients with different amounts of lipids. Acta Derm. Venereol. 1992 72 327-30. 

Leveque, J.L., Dresler, J., Ribot-Ciscar, E., Roll, J.R, and Poelman, C. Changes in tactile spatial discrimination and cutaneous coding properties by skin hydration in the elderly. J. Invest. Dermatol. 2000 115 454-8. 

Mixtures of sugars, saccharide isomerates, have been shown to be effective humectants. These isomerates mimic those found naturally in skin as a result of the hydrolysis of glucosylceramides. In clinical studies Smith113 has shown that these isomerates reduce the visual appearance of dry skin, increase skin hydration, and reduce stinging to lactic acid. 

Hara, M., Ma, T., and Verkman, A. Selectively reduced glycerol in skin of Aquaporin-3-deficient mice may account for impaired skin hydration, elasticity and barrier recovery,./. Biol. Chem., 277, 44616, 2002. 

Different types of evidence exist for the clinical efficacy of 10% urea in the treatment of psoriasis (Table 19.1). Early clinical data from a clinical study on various types of hyperkeratosis showed no superior effects on from 10% urea cream compared to ordinary aqueous cream BP in the treatment of psoriasis.10 However, five psoriatic patients with chronic therapy-resistant lesions obtained soft and pliable skin after treatment with 10% urea, but no effect on erythema was observed.17 Psoriatic lesions on the extremities (at least 5 cm in diameter in size) also showed clinical improvement after two weeks of treatment with an ointment containing 10% urea (Basodexan S ointment) in a placebo-controlled study on ten patients.26 Higher values of skin capacitance (suggested to reflect skin hydration) were also noted on urea-treated areas. Increased hygroscopicity and water content were also obtained after treatment with 10% urea ointment in patients with psoriasis vulgaris.27 Moreover, urea treatment reduced epidermal proliferation, measured as an altered expression of involucrin and cytokeratins.26 Treatment of psoriasis vulgaris with 10% urea-formulations support clinical efficacy at evidence-level lb (cf. Figure 19.1). 

A 5% urea cream (Canoderm , ACO Hud AB, Sweden) increased skin hydration (measured as capacitance)34 and showed similar efficacy as a 4% urea cream also containing 4% sodium chloride as active ingredient (Fenuril , ACO Hud AB, Sweden) in a double-blind, randomized, and parallel study on 48 atopic patients.35 The clinical and instrumental assessment showed improvements in both groups during the treatment period.35 In another study on atopic dry skin, the 4% urea-formulation... 

Open, uncontrolled Urea formulations increase skin hydration 37... 

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