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products can help prevent and relieve these problems.15 Fresh wounds usually show a neutral or
alkaline pH level. If not properly treated, the elevated pH may enable the formation of biofilms that cause difficult-to-treat wound infections. Since different phases of wound healing are also depending on specific pH conditions that determine the activity of the immune cells and key enzymes, health professionals and their patients can profit immensely from close pH monitoring and acidic treatments, especially for chronic wounds.15,16
With the increased hygienic requirements
in COVID-19 times, skin impairment that was formerly restricted to special professions requiring frequent washing, such as health care workers, has become more common even for other population groups. Excessive and sometimes over-enthusiastic
hand washing since the upsurge of COVID-19 has led to a significant increase of self- reported or diagnosed hand eczema in the general population. Dermatologists state that they are confronted with a raise in skin problems since these intense hygiene practices have been recommended for everybody.11,12
The importance of local pH value Not only on the skin surface, but also within the stratum corneum, the local pH value is of immense importance. Getting more and more alkaline towards the base of the stratum corneum, it provides the triggering conditions for enzymatic action and differentiation processes in different depths, for example the transformation of ceramides, free fatty acids and cholesterol that are important components for a healthy skin barrier function.17-19
Even the desquamation of
corneocytes at the skin surface is dependent on a specific pH value.20 The fact that darker pigmented skin shows
a more acidic pH value is explained by the pH-lowering effect of melanin and a higher expression of secretory phospholipase A2f (sPLA2Af). A lower pH value for these skin types leads to an increased epidermal lipid content and lamellar body density, thereby providing a superior permeability barrier function.21
With the stratum corneum pH being a
central regulator of skin barrier homeostasis and at the same time an effective defence mechanism, it is a major parameter in several pathogenic skin conditions. In atopic dermatitis, it links skin barrier dysfunction, an altered immune response and unfavourable environmental conditions.22
Evidence also
points to an involvement in psoriasis.23 Specific forms of ichthyosis show a different
pH gradient within the skin, compared to other ichthyosis types and healthy skin.24
Subclinical
inflammation in acne-prone skin might also be linked to changes in skin surface pH.25 All of these findings underline the
importance of the pH value on the skin surface and of its gradient within the stratum corneum for a healthy skin function and protection. Therefore, pH measurement is a critical parameter to understand skin health and possible problems. Especially for the very young and the elderly and for all people suffering from
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impaired skin conditions, manufacturers need to master the galenic challenge of developing suitable cosmetic products with a rather acidic pH value, at the same time offering a high buffering capacity for the correction of pathologic pH conditions.26, 27 Combining the acidic product pH with
an optimal mix of surfactants, will enhance product compatibility and minimize skin irritation and intolerance.28
pH changes at the
skin surface after application of such products offer insights in the compatibility of the product. Also, for hair and scalp, the pH is an
important parameter. The scalp pH ranges about 5.5, and the hair shaft pH is even more acidic.29
Using shampoos with an alkaline
pH may not only impact the scalp condition but also lead to a swelling of the hair shaft and thereby to a loosening of the protective cuticle.30
April 2023 PERSONAL CARE
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