Total water content (hydration), elasticity, pH and sebum levels were selected as the most representative indices of beneficial effects. It is well known that hyaluronic acid can bind with up to 6 L of water in vitro to a point of maximal saturation, thus becoming fundamental for biology and a functional determinant in cellular water homeostasis.

The statistical analysis evidenced a significant positive effect of filler treatment and a significant improvement of all the parameters measured with Skin Tester before and after the procedure.

The results suggest that filler injection significantly improved the quality of the skin, mainly in terms of total water content, elasticity and sebum, with a slight increasing trend after treatment.

In particular, pH decreased from basic values to neutral values in all the subjects except for two people who had the same parameters before and after the procedure. Skin elasticity increased significantly in all 20 patients owing to the action of hyaluronic acid, which instigates collagen production and consequently, a significant change in skin tensile strength. Skin hydration reached optimal values as hyaluronic acid attracts and holds water molecules. Finally, a sebum improvement was also observed and it was correlated with a decrease of pores squeeze and inaesthetic skin.

A limitation of this study was the absence of a follow-up over a long-term period (at 6 months, for example). With this in mind, the authors plan to undertake further studies to include long-term follow-up.

However, this study has demonstrated that hyaluronic acid injection can actually significantly improve skin parameters such as hydration, elasticity, pH and sebum.

Discussion and conclusions

The Skin Tester system is very easy to use, quick and gives accurate computer-assisted information that can be stored and printed at any time. It is a reliable and useful tool for clinical investigations in different medical and surgical branches (e.g. dermatology, vascular surgery, gerontology, gynaecology, plastic surgery).

The tested instruments gave the authors the opportunity to standardise skin pathology in different clinical conditions, with the chance to record all the relevant data measured on each patient at planned time intervals, or after medical surgical treatment.

Skin Tester represents an updated, exhaustive functional and rational solution compared with some of the other devices, as it is based on modern physical principles such as diagnostic ultrasound and plethysmography and therefore, it meets all the required criteria to perform a simplified and standardised holistic investigation.