Читать книгу pH of the Skin: Issues and Challenges - Группа авторов - Страница 15

The use of liquid or semi-solid wash-off or leave-on preparations to clean or treat the skin has a long tradition. The term “cleanser” – first mentioned in 1955 in Medline – is most often used in connection with removing make-up, dead skin cells, oils, dirt, and other types of pollutants from the skin of the face [44]. Today, the term is used in a more general way. Based on the anticipated beneficial effects of acidification of the skin, it became popular to develop slightly acid cleansers to add an additional benefit to the cleansing products [44, 45]. Nowadays, soap-free, skin-friendly cleansers are most often commercialized with slightly acid or physiological pH values (≈5.5). Despite the fact that the majority of investigations confirmed the benefits, some conflicting investigations exist. Duncan et al. [46] demonstrated that a product used (pH 5.5) in routine skin care significantly affected the skin pH of ICU patients but not the bacterial colonization. In a long-term study (5 years), Takagi et al. [47] found that the continuous use of a soap-based cleanser did not affect the pH-maintaining mechanism of human skin. From the beginning on, it was also clear that additional factors than just pH may affect local tolerance [48–51].

More recently, the potential of semi-solid leave-on products to “correct” the skin surface pH and hence to accelerate barrier recovery, to maintain, or to enhance barrier integrity has again attracted attention (note that Scholz already reported in 1930 the potential of acid treatments of skin diseases [16]) [52–56]. The studies consistently showed accelerated barrier recovery and enhancement of the barrier integrity and properties. By means of tape-stripping the stratum corneum, Behm et al. [54] also reveal the data that the pH in the deeper layer of the skin (stratum granulosum) was actually lowered after the use of a pH 4 O/W emulsion with sufficiently high buffering capacity. Indications such as incontinence-associated dermatitis or atopic dermatitis are medical highly relevant skin conditions with a great level of affliction that urgently need treatment options. Products for targeted skin acidification may offer in these indications new therapeutic options [56–58]. However, further clinical trials with larger cohorts are necessary to strengthen these findings. Important issues related to formulation composition (acids), buffering systems used, or buffering capacity of product and product dosing have so far not been directly addressed.