A Commercially Available Skin Care Lotion with a pH of 4.5 and 10% Urea Improves Skin Surface pH, Stratum Corneum Hydration and Epidermal Barrier Function in Subjects with Dry Skin and Atopic Diathesis
OBJECTIVE:The physiological skin surface pH is crucial for several epidermal
barrier functions, like stratum corneum integrity, cohesion and restoration.
Alterations of the “normal” acidic nature of the skin surface have been shown
to correlate with specific skin conditions like aged or inflamed skin and are
leading to impaired skin barrier function and formation. It is previously
demonstrated that topical acidification in atopic dermatitis improves stratum
corneum function, skin barrier structure and clinical signs in dermatitis.
Against this background, we examined the impact of a slightly acidic skin care
product containing urea on stratum corneum hydration, skin surface pH and
epidermal barrier function in subjects with dry skin and atopic diathesis. METHODS: Stratum corneum hydration, skin surface pH and transepidermal water loss were
biophysically measured before and after a 4-week treatment period with the test
product (pH 4.5, 10% urea) compared to the reference product in 25 volunteers.
In addition, dynamic epidermal barrier parameters like stratum corneum
integrity, cohesion and recovery were investigated by using a previously
described tape stripping approach. RESULTS: It was shown that the test
product (pH 4.5, 10% urea) significantly elevated stratum corneum hydration and
improved the acidic nature of the skin surface by lowering the skin surface pH
to a greater extent compared to the reference product. After the 4-week
treatment period a significant faster barrier restoration was detected on the
test site treated with the test product compared to the reference product.
Moreover, the test product strengthens the skin barrier integrity and cohesion. CONCLUSION: The present marketed skin care lotion was shown to increase
epidermal barrier function after 4 weeks of application. Balancing and
controlling the skin surface pH in subjects with dry and atopic-prone skin by
application of the herein tested o/w emulsion with a given pH of 4.5, in
combination with a 10% urea content seems to be effective and beneficial. The
results are important for the formulation of topical products for dry and
atopic-prone skin.
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