Current problems in dermatology最新文献

The act of birth and the growth of an infant in consecutive months are critical for the baby's adaptation from intrauterine life to the relatively dry and gaseous environment. These adaptive changes have not only effects on structural components but also subsequent functional consequences. The formation of acid mantel is important for the integrity and cohesion of the stratum corneum, a key component of an intact epidermal barrier, as well as for multiple defensive functions of the skin. In this chapter, we review the mechanisms in pH development after birth. Furthermore, we focus on different factors affecting skin surface acidity formation such as the pre- and postnatal age and weight, gender and anatomical site.

Regulation of pH is one of the most complex mechanisms in human physiology. Indeed, the H+ ion concentration not only contributes to the establishment and maintenance of the body's homeostasis (by defining isohydria) but it also acts as an ionic, electric or osmotic driving force; provides optimum conditions for the proper functions of a plethora of molecules; behaves as an extra- and intracellular signaling system; exerts protective functions, and so on. The versatile role of pH requires delicate, well-orchestrated regulatory machineries that are controlled by a multitude of endogenous mechanisms - this is especially true for the skin whose pH is quite unique within the body. In this chapter, we summarize key endogenous factors and mechanisms that can influence the pH of the skin. Moreover, we highlight the significance of certain molecular systems (i.e., pH-sensing ionotropic and metabotropic receptors) that have recently emerged as potential "pH-regulated sensors and transducers," which are suggested to mediate the cellular effects of pH in various skin compartments and cells.

Several studies have generally described the existence of differences of skin surface pH according to gender, age, and ethnicity, but these studies have reported inconsistent results, depending on anatomical sites, methods, and time of measurement. Overall, it could be summarized that female sex, younger age, and black skin have a lower skin pH compared to male sex, older age, and white skin.

During aging, the pH of the epidermis goes up and the calcium gradient goes down. Both have negative effects on the protective function of the epidermis and both are connected to each other as is discussed here. In the aging process, the pH rises from ∼5 to ∼5.5-6. The establishment of the skin pH is the joint effort of several independent factors including the activity of sodium-hydrogen antiporters and the presence of lactate, urocanic acid, free fatty acids and melanophores in the outermost layers of the skin. All these elements are under the control of a small ion: calcium. Calcium is organized in the form of a gradient in the epidermis with low concentrations in the stratum basale and peak concentrations in the stratum granulosum. During the aging process, this epidermal gradient collapses. In this chapter, we describe how a drop of calcium in the stratum granulosum affects the expression as well as the activity of proteins and enzymes that are involved in the establishment of the skin pH. This rise of the pH combined with a rearrangement of the cornified envelope is a main driver for a reduced epidermal barrier in old age leading to an increased prevalence for infections, reduced resistance against mechanical stress and reduced wound healing.

The acidic nature of the skin surface was recognised more than a century ago and has been measured since 1928. Several non-invasive methods for measuring skin surface pH have been developed ever since and have contributed to our understanding of healthy and diseased skin. This chapter summarises the endogenous physiological, exogenous and environmental factors that influence skin surface pH and its measurement as well as the different measurement methods for skin surface pH, with specific emphasis on the classic planar glass electrode method. Also, practical guidance for measurement of skin surface pH using the planar glass electrode method is provided. Adherence to practical skin surface pH measurement (method) guidelines with due consideration and practicable control of all factors that may affect skin surface pH will ensure credible pH measurement results in our continuous pursuit of understanding especially diseased skin.

In order to maintain skin in "good condition" one can use cosmetic products. Importantly, those skin care products should fulfil specific requirements for specific life phases and specific skin conditions. In this review, we focused on 2 different age groups - namely, infants and the elderly - as well as on 2 specific skin conditions occurring in both age groups - very dry skin (Xerosis) and hyperhydrated skin (diaper rash). The goal in both conditions should be to maintain skin surface in its physiological acidic state, which is in turn crucial for the permeability barrier function, stratum corneum integrity/cohesion and antimicrobial defense. Skin care products formulated with an effective buffer system at a more acidic pH, for example 4, may be the best option to improve the acid mantle and skin barrier function and thus keep the skin in "good condition."

Not much is known about the role of skin pH in skin pathophysiology, in particular in psoriasis. However, there is compelling evidence that the epidermal pH can influence the skin homeostasis and affect the skin barrier by changing the activity of cutaneous enzymes and through the modulation of skin inflammation and microbial colonization. This includes the activation of secretory phospholipase A and interaction with the peroxisome proliferators-activated receptor and retinoid pathways. In addition, pH in skin affects the activity of aquaporins and this controls the hydration of the epidermis. Changes in skin homeostasis, differentiation, barrier defects, and inflammation play a crucial role in the pathogenesis of psoriasis. There is evidence that skin pH can affect all of these important factors. However, more studies are needed to examine objectively and precisely the pH in the various skin layers in psoriatic lesional and non-lesional skin and compare it to normal skin. This additional know-how is essential to understand the role of skin pH in psoriasis with ultimately great potential of manipulations of skin pH for topical approaches in the management of psoriasis.

The body skin pH can usually vary from 4.0 to 7.0 depending on location. The presence of natural acidic compounds on the skin surface helps maintain the skin's physicochemical properties as well as its protective functions. Since the slightly acidic pH of the skin is extremely important for the skin's protective function, the skin is widely known as "acid mantel." Factors such as age, race, gender, body sites, biochemical differences, and even washing affect the pH of the stratum corneum. Recent clinical studies using an emollient-base finish product using the traditional way of measuring skin pH produced results that indicated an apparent increase in skin pH. The apparent pH increase with these products is most probably an artifact of the skin pH measurement technique. Our findings show that certain petrolatum-based emollients and components could create a protective barrier and help maintain the healthy acidity of the skin. Our work provides new evidence of emollients helping to stabilize skin pH in its natural balanced state rather than affecting it. This new learning should be taken into consideration by other researchers in the area of skin pH as well as in clinical studies to avoid misleading results.