Materials and methods

For an objective assessment of the quality of the skin in cosmetic medicine, it is relevant to perform qualified clinical investigations with pre- and post-treatment comparisons in order to support the patient’s judgement with the instrumental detection of skin parameters. Therefore, the authors developed a non-invasive multi-parametric point of care diagnostic tool (Skin Tester, manufactured by Selenia Italia and distributed by Dermal Institute), to provide an evaluation of a number of skin parameters, such as hydration, pH, elasticity, and sebometry.

Skin Tester

Skin Tester is a new device originally planned and validated by the authors in comparison with the currently available skin analysers for the diagnostic qualitative analysis of facial skin. It analyses a number of parameters to monitor pre- and post-treatment variations. An ultrasound emitted beam is reflected by the dermal tissues, according to its stromal density and vascular tone. Furthermore, impedance variation as related to intracellular and interstitial water content and photoplethysmography, a reflectometric method to evaluate vascular network dynamics, are encompassed by the diagnostic device. Therefore, the following skin parameters can be detected:

  • Total and intracellular water to correctly evaluate hydration
  • Extracellular water and water retention to detect tissue fluid engulfment and drain impairment. The stratum corneum has a water content which is balanced by general skin and subcutaneous tissue hydration
  • Skin pH, related to sebaceous and sweat gland secretion. Skin pH is usually slightly acidic as a result of lactic acid, amino acids and fatty acids coming from sweat, sebum, and degradation products of the corneal layer, which supplied amino acid and pyrrolidinecarboxylic acid.

The pH measuring device is a potentiometer with an electrode sensor, with selective hydrogen ion sensitivity. The small amount of water lying between the electrode and the skin surface is adequate to solubilise ions on the skin’s surface and create adequate measuring conditions.

When the pH probe is in contact with a solution containing H3O+ ions, a flux of electrons moves between the active electrode and the reference electrode. The potentiometer then measures the difference in potential, which is directly proportional to the pH of the solution used during examination:

  • Thickness of the horny layer
  • Sebum epidermic concentration, a thin hydrolipidic film produced by the sebaceous glands
  • Skin elasticity and tonicity parameters, related to elastin, collagen and GAG imbalance
  • Vascular network adaptations.

The Skin Tester works very quickly (30 seconds) and records the operative data through a touch-screen display. It has a flat transducer to be applied over the skin surface and requires a gel film to achieve ultrasound delivery. Analysis results are printed on a ticket with the reference values, so the doctor and patient can keep a record of the cosmetic treatment variations.

Investigation of dermatological and cosmetic parameters

Filler injections

The authors report on their first clinical experience using the Skin Tester device in cosmetic medicine, investigating on a series of cases, the individual healing process of which could be adequately monitored.

Twenty patients (14 females and six males) aged between 19 and 67 years were admitted to this dermatologic evaluation, before and after the injection of dermal fillers (specifically Aliaxin GP, Ibsa Farmaceutici, Italia). This study was performed in accordance with the Helsinki declaration and local internal review board (IRB) rules. All patients signed an informed consent after reading the standard information sheet and discussing the procedure with the clinician. Doses of 1–2 ml of hyaluronic acid were injected at different facial areas, according to the individual patient’s needs, including nasolabial folds, upper lips, chin, periorbital area and cheeks. The injection volume was selected at the discretion of the specialist, administering the compound until full correction was achieved.

A pre- and post-treatment measure of skin parameters (hydration, elasticity, pH and sebum levels) helped the authors to define the real amount of filler required to reach an optimal cosmetic effect, by evaluating the skin response immediately after the procedure.

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