Placebo-controlled, double-blind, randomized, prospective study of a glycerol-based emollient on eczematous skin in atopic dermatitis: biophysical and clinical evaluation

Background/aims: Atopic dermatitis (AD) is a frequent, chronic inflammatory disease influenced by local, immunological, genetic and environmental factors. Important symptoms of AD are dry skin, intense pruritus and impaired epidermal barrier function. The therapeutic management of AD is difficult and needs individualized concepts. Moisturizing creams and emollients are useful and important treatment adjuncts for the daily skin care of patients with dry and inflamed skin, e.g. AD. Glycerol is known to increase stratum corneum (SC) hydration, improve epidermal barrier function and decrease clinical signs of inflammation. However, no controlled study on the efficacy of glycerol on barrier function and SC hydration in AD has been published. In the present study, a topical 20% glycerol preparation was compared with its vehicle in patients with AD. The aim of the present study was to evaluate the effect of a single emollient ingredient in AD within the full frame of a phase III drug study.

Methods: 24 patients with AD were treated for 4 weeks twice daily with a glycerol-based emollient in a randomized, double-blind study. Transepidermal water loss, skin capacitance, erythema and skin surface pH were assessed with biophysical, non-invasive instruments. The SCORAD and a local severity score were evaluated. After a wash-out period of 2 weeks, these parameters were assessed in order to quantify the sustained effect of this treatment.

Results: SC hydration was significantly improved, and epidermal barrier function was restored under treatment with glycerol-containing cream compared to the glycerol-free placebo. No significant differences were detectable for erythema values, SCORAD and local severity between the glycerol-containing cream and placebo. However, an improvement over time was detectable in the assessed parameters in both groups indicating the importance of emollient treatment in AD.

Conclusions: Glycerol-based emollients have a positive influence on the skin of patients with AD. They enhance the SC hydration. Furthermore, it was possible to evaluate skin care products with a protocol design for efficacy studies of fully registered drugs in a placebo-controlled study.