A short history of Dermatest®

DERMATEST GmbH was founded in 1978 in Muenster, Germany by Dr. med. Werner Voss, M.D, specialist for dermatology, venerology and allergology, who has been managing the company since then.

The main focus of DERMATEST GmbH is validated medical and dermatological research methods in connection with internationally accepted allergologic test methods.
In connection with the daily practice of a dermatologist new test designs have been developed, e.g. in cooperation with ophthalmologists and dentists.
Methods derived from dermatological research were converted into everyday tests, e.g. profilometry (1991).
The connection to dermatological practice allows a strong synergistic effect for tolerance and efficacy studies of cosmetics, e.g. the selective inclusion of test persons of determined characteristics: toddlers, persons with sensitive skin, atopic dermatitis or acne vulgaris.

This is not only useful for the fast recruiting of test persons, but even allows the collection of specific test panels.

Portrait of Dermatest®

Services

Dermatest, a medical research company, was founded in 1978. For more than 25 years we have been carrying out tests and clinically controlled in-use tests on cosmetic and pharmaceutical products. For determination of product tolerance and checking the effectiveness of cosmetic ingredients we offer a wide range of test types:

• Patch tests
• Repetitive patch tests
• Photo-patch tests
• in-use tests for dermatological, ophtalmological and dental products to test their tolerability and efficacy
• market research concerning acceptance and customer satisfaction regarding the tested products
• Skin-roughness tests according to DIN
• Light protection factor measurements according to DIN and COLIPA
• UVA protection factor measurements according to the Australian Standard
• Skin moisture determination by corneometer measurement
• Ultrasonic examination of the skin (Dermascan C)
• Examination of the skin by confocal laser (Vivascope)
• TEWL measurements by evaporimeter
• Sebumetry
• Skin elasticity determination by the cutometer
• Optical 3D analysis (PRIMOS)
• Hair growth analysis by TRICHOSCAN

Because of our close contact with patients in our daily work as practitioners we are able to recruit test persons for very special questionsm e.g. products which should be labelled especially for sensitive skin are tested on persons with atopic skin in the eczema-free interval.

We also cooperate with other medical disciplines. In the case of testing eye make-up we consult ophtalmologists, in the case of testing bleaching ointments for the teeth we cooperate with dentists.

All test procedures are under the supervision of a specialist for dermatology and are evaluated and documented.

Besides our clinical in-use tests and our dermatological and allergological tests we offer:

• literature research
• presentations and workshops on dermatological subjects
• safety assessments according to EG guidelines

Technical equipment

1. Skin Elasticity

Measurements for skin elasticity are made with a cutometer. The measurement is done with an instrument which, using the vacuum principle, sucks up a defined area of skin surface and records it optically. Analysis of the recorded measurement curves makes it possible to determine the elastic and plastic characteristics of the skin. Young skin shows a high degree of elasticity and loses shape only gradually while regaining its original state after the end of the suction procedure. Skin which is healthy, supple and adequately moist will have a higher elasticity than a dry, rough skin. The cutometer therefore gives a set of measurements which allows us to quantify elastic characteristics.

The tests for skin elasticity are carried out by a DermaLab® Systems cutometer, supplied by Cortex Technology, Denmark. The calculation of the elasticity modulus (Youngs Modulus) (P. G. Agache, 1995) is based on the differential values which are necessary to raise the skin surface 1.5 mm between two infrared detection degrees within the measuring instrument and is worked out using all the instrument constants.

The instrument is secured by an adhesive ring to the area of skin to be examined so that there is no possibility of it moving during the procedure.

2. Profilometry with primos

In the Primos optical 3D skin measurement device, the so-called digital stripe projection technique is employed as optical measurement process. With this measurement method, a parallel stripe pattern is projected onto the skin surface and depicted on the CCD chip of a camera. The 3D measurement effect is achieved by the fact that minute evaluation differences on the skin surface deflect the parallel projection stripes and that these deflections constitute a qualitative and quantitative measurement of the skin profile. The skin profiles are recorded by the CCD camera, digitised, and transferred to the measurement and evaluation computer for qualitative evaluation.

Compared to conventional optical 3D measurement facilities based on stripe projection, the optical 3D in vivo skin measurement device Primos ("Phaseshift Rapid In Vivo Measurement Of Skin") has the advantage that, analogously to digital signal processing, a digital light and/or stripe projection is employed. The digital light projection used is based on developments of digital micromirror projectors. This technology yields a series of advantages particularly when applied to optical 3D in vivo skin measurement, resulting from the fact that the light intensity is high and can be controlled point and/or pixelwise, and the possible exposure time is very short.

This is extremely helpful in the determination of skin roughness or skin smoothness and is of great importance, e.g. when in the framework of a cosmetics study the effect of creams in respect to smoothing effects on the skin or the reduction of wrinkles is to be examined and assessed.

3. Determination of SPF

Furthermore, our company offers determinations of the sun protection factors according to different methods, e.g. the European Standard (COLIPA) and the Australian Standard.

COLIPA

The COLIPA sun protection factor test method is a laboratory method which uses an artificial ultraviolet (UV) light source with a defined and known output. In the test, a stepped series of delayed UV erythema (reddening of the skin as a result of superficial vasodilation) reactions is induced on several small areas of skin of the selected test persons. The test persons must attend the test laboratory several times: on the first occasion, they are exposed to the necessary UV doses to find out the MED (Minimal Erythemal Dosage), on the following occasion the delay in erythema reactions caused by the sunscreen product and using an identical test arrangement is assessed.

The gradual increase in the UV dose causes different degrees of skin erythema, which reaches a maximum approximately 24 hours after UV exposure. The exposure time which produces erythema of unprotected skin types II and III (according to Fitzpatrick) is usually about two minutes with the selected radiation. The lowest dose which produces an area of unambiguous erythema is the minimum erythema dose or MED. The MED for unprotected skin (MEDu) and the MED after application of a sunscreen product (i.e. the MED. for protected skin = MEDp) are determined simultaneously on the same test person. The MEDu and the MEDp can be evaluated visually by trained personnel or instrumentally by a colorimeter. Several products can be tested on the same person at the same time.

The sun protection factor of the product is calculated for each test person on the basis of the relation between MEDp and MEDu. A product must be tested on at least ten persons. The COLIPA sun protection factor test method also defines a standardised procedure for the application and distribution of the sunscreen product on the test areas of the skin as this phase of testing has been identified as a main source of experimental error.

In all tests, a standard product according to COLIPA with a correspondingly high or low sun protection factor depending on the anticipated sun protection factor of the test formulations should also be used, to avoid greater mistakes.

Light protection according to the Australian Standard

The percentage transmittance of UVA radiation is measured between wavelengths of 320 and 360. The Australian Standard is fulfilled when up to 10 % of the UVA light is transmitted to the skin.

4. Corneometry

With the corneometer principle, the skin moisture of the outer layer of the skin (Stratum corneum) is determined by means of a capacity measurement. This principle is based on the fact that the dielectric constants of water and other materials are different. A relevantly shaped measuring capacitor reacts with differing capacity changes to the measurement volume that the probe has been placed on, that the equipment automatically recognises and evaluates. The active probe that is coated in special glass is pressed against the skin position to be measured and after one second the value is displayed on the corneometer as well as the percentage of moisture on the upper skin. Special construction guarantees that the active forepart of the probe is always pressed down with constant pressure, even against any inadequate skin positions.

The corneometer consists of a desk housing and an associated probe. This is connected to the desk housing that has a special socket for the helix cable. In the desk housing the measured values are displayed to a maximum of three decimal places. In addition to this, the display also fulfils other information functions.

The measurement sensor is of rectangular shape. The special glass coating on the active forepart can be moved axially and has a stroke of at least 3mm. The measuring principle requires the plane of the forepart to lay with constant pressure against the skin. In order to guarantee the best reproduction of this, the forepart of the measurement probe has to be very small (7 x 7 mm). The internal moving part - the active forepart - is pressed against the skin by a spring which is always at 3.5N.

The corneometer works completely automatically. The value displayed on the corneometer gives the degree of moisture on the surface of the skin, e.g. before and after the skin was treated with cosmetics or pharmaceutical products, i.e. the unit displays the status or the change in the moisture on the surface of the skin.

5. Ultra-sonic measurement (Dermascan C)

Changes in the thickness and density of the skin can be objectively documented using ultra- sonic measurement. A 20-MHz-ultrasonic device is normally used for this purpose.
We define ultrasonic waves as frequencies above the human hearing range in a range from 16kHz to 1GHz. Using the 20-MHz ultrasonic device it is possible to reach a high standard of definition of cutaneous and subcutaneous structures.
Using an axial resolution of about 80 µm and a lateral resolution of 200 µm, structures up to a depth of one centimetre can be displayed. This procedure displays evidence of organ measurements (for instance thickness of the skin) and its changes, tissue structure and changes (collagen structure) and also the presence of moisture.

Ultrasonic diagnostis supports the recording and analysis of the signal, which using the interaction between body and ultrasonic waves provide results.
This diagnostic procedure produces no tissue damage or any radiation exposure whatsoever. It is also painless and non-invasive. The ultrasonic process is also suitable for clinical monitoring, because of the reproducable results and also simultaneous comparison with other test persons. However, the tester must be very experienced and this method of testing is also extremely time-consuming.
Different structures can be illustrated in different ways. The A-mode (amplitude mode), which gives information only about one axis through the body, is a direct presentation of the oscillation amplitude of a single reflected sonic signal. The B-Mode (brightness mode) is the two-dimensional image of the amplitude of the modulated brightness. A-mode signals and multiple A-scans and allows a more vivid presentation of echo structures due to the detection of topographical correlations. The C-Mode (computed mode) describes the cross-section of the skin parallel to the skin surface. The M-Mode (motion mode) describes temporal changes of an A-Scan in a constant site documented as a B-Scan image.

The performance of the ultra sonic device can be judged by the local display definition. The display definition produces the smallest possible separation distance between two points that can be measured.
Axial resolution is measured by the length of the sonic impulse and the wave length or frequency. The gauge of radiation of the scanner head defines the lateral resolution and depends on the frequency and diameter of the oscillator. A further parameter is the contrast resolution capability which provides information on the structural differences in tissue characteristics. This depends on the velocity of the sound waves. Because of the proportional difference between sound weakening and sound frequency the depth of penetration decreases at high frequencies. The picture quality is influenced by the dynamic area and the picture frequency of moving objects.

Healthy skin provides a high entry echo, which originates through the high impedance difference between the forward section range (water) and the epidermis. The amplitude of the entry echo is not equivalent to the thickness of the epidermis. At higher frequencies (> 50MHz) and in the area of the skin of the plantar and the palms stratum corneum and stratum malpighii produces a low echo and is separated due to a strong echo line (impedance difference between xeric stratum.corneum and stratum Malpighii with a high content of water). The entry echo overlays the low-echo epidermal layers if the 20 MHz-ultrasound is used and if the corporal skin is examined.
With time-dependent skin thickness measurement, the following should be taken into consideration: temperature, time of day, hormonal influences (menstrual cycle) and so on. Research should always be made under the same conditions.

This presentation is just meant to give you a short overview of our technical equipment and our company work. It is far from complete but we hope you have gotten a first impression and we have succeeded in gaining your interest.