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.

Treatment of Aged Skin with a pH 4 Skin Care Product Normalizes Increased Skin Surface pH and Improves Barrier Function: Results of a Pilot Study

The physiological skin surface pH is just below 5. With age the skin surface pH increases up to 6. An increased pH correlates with reduced barrier integrity/cohesion. The present pilot study assesses possible normalization of an increased skin surface pH of the elderly and improvement of barrier function via application of ≈pH 4.0 skin care products. Baseline skin surface pH was determined in elderly (80+ years old;n = 15) compared to middle aged adults (31 - 50 years old;n = 15). The effect of o/w emulsions at pH-values of 3.5, 4.0, 4.5 and 5.5 on the skin surface pH was determined in both groups. Further, the effect of a 4-week treatment with a pH 4.0 skin care product on the skin surface pH, skin hydration and barrier integrity was assessed. Thirteen elderly females were involved in this home-in-use test. Increased baseline skin surface pH of the elderly normalizes to the physiological pH of 4.5 - 5.0 over 7 hours after single application of o/w-emulsions with a given pH of 3.5 or 4.0. A 4 week treatment employing the pH 4.0 skin care product improves the epidermal barrier integrity of the elderly significantly (p = 0.005). Reduction of the increased baseline skin surface pH of the elderly is accompanied by improved epidermal barrier integrity. Skin care products for the elderly have to be adjusted in the pH range of 3.5 to 4.0.