In the natural process of skin renewal, corneocytes desquamate from the surface as single cells or small scales. Insufficient desmosome degradation leads to conglomerates, that become visible as large scales, resulting in a dry and rough skin appearance. Adhesive discs are an important tool for visualizing dry and flaky skin and can be used to assess the effectiveness of skin care products, because the care of dry skin contributes to holistic well-being.

Two scientific methods of assessing the effects of skin care products on skin condition regarding desquamation – infrared densitometry and visual expert assessment – were compared to determine whether greater gradation through intermediate levels in the visual assessment indicator scale provided more differentiated results.

In a blinded long-term panel study of 31 female volunteers with dry and normal skin, adhesive discs were used to quantify the stratum corneum scaling by infrared densitometry. The same discs were then used for visual assessment by an expert who rated the extent of desquamation via an indicator scale from 0 to 4 with 0.5 intermediate steps. Desquamation was evaluated before and after four weeks of twice daily treatment with three skin care products on the forearms compared with an untreated control.

After four weeks of product treatment, both the densitometry and the visual expert assessment showed a significant improvement compared with baseline and untreated. However, the expert assessment based on intermediate steps also revealed differences between the products. Based on the p-values and percentage improvement rates of subjects, as well as the improvement rate compared with untreated, the expert assessment showed a statistically more significant result than the densitometry.

While both methods showed a significant change in skin condition, the visual assessment with intermediate steps showed more differentiated or significantly stronger results and therefore enables a more precise gradation of skin conditions.