Cosmetic Testing Equipment: Device and Types of Equipment for Dermatological Evaluation for Women’s Skin

Arushi Saloki¹, Taranjeet Kukreja¹, Sarita Gaikwad¹, Arvind Kumar¹, Ayush Parker¹, Bhavana Dowand¹, Chetna Sahu¹, Damini Mali¹, Swarnlata Saraf^1*

¹University Institute of Pharmacy, Pandit Ravishankar Shukla University, Raipur 492010, Chhattisgarh, India.

 Abstract:

There are many different equipment and techniques for an aesthetic skin evaluation, efficacy testing, claim support, and objective measurements of women’s skin parameters for all applications. Women have softer skin than men. Nothing commercially available in terms of moisture, oiliness, color, texture, etc existed over 20 years ago. Fortunately, several cost-effective ways are available to quantify these characteristics and compare them before and after a treatment or application. Before distributing the finished product to outside testing facilities for the final validation, the cosmetic business conducts these tests at different stages of product development to determine the product’s direction. In this review, we have summarized the C+K devices that are acknowledged as industry-standard tools for assessing efficacy in the fields of cosmetics and the types of equipment used for the cosmetic evaluation of the skin.

 Keywords: Cosmetic equipment, types of equipment, evaluation, skin parameters, dermatology.

 Introduction

Cosmetics must be examined during production to ensure that they meet product specifications, are safe, and are made economically. Sensory approaches have been used from the earliest to establish sensory evaluation methods for objectively understanding users' impressions. Although the only instrumental method cited was a spectrometer to detect sunscreen chemicals, an article on dermatologically efficacy testing was published in the Society of Cosmetic Chemists' first publication, which was published in 1947. 1956 was the year that the first instrumental method of measuring the static charge on human hair was published. The in-vitro method using radioisotopes to measure absorption by hair was also published in the same journal. The development of the means of measuring cosmetic effects is driven by increasing pressure on cosmetic companies to provide solid evidence to support claims made for products. The development of the means of measuring cosmetic effects is driven by increasing pressure on cosmetic companies to provide solid evidence to support claims. Claims associated with several of the signs of aging such as reduced facial wrinkling are often subjected to intense scrutiny. Other claims include increased moisture level in the skin, improvements in skin texture, elasticity, and, smoothness, and of regulation of sebum. (Ctplus 2022)

The C+K devices are recognized as industry-standard methods for evaluating efficacy in the sectors of food, nutritional supplements, personal care products, raw materials, medications, and cosmetics. The devices are easy and quick to use, thus perfectly suitable to study the product properties on the skin in each phase of the development process. The C+K equipment is used by CROs and external testing labs all over the world to conduct final product tests for documentation.

Cutometer

Since the cutometer Probes are modular, we can assemble them anyway we need to. They are made up of probes and a basic apparatus. By selecting a simple device that satisfies our needs, such as one with a display, one that can only be connected to software, or even one that can wirelessly communicate measurement information to software. Selecting the measurement parameters that are necessary for your work. The basic gadget and the probes will work together to create your measuring center. (Does et al. 2017)

Fig 1: Cutometer® dual MPA 580 Device

The Cutometer Probe Family

The Cutometer probes are digital and contain all calibration information. Thus, they can be simply connected to a basic unit. A variety of probes are available to measure different parameters on the skin:

A.       Corneometer® CM 825: Skin surface hydration

B.       Sebumeter® SM 815: On the skin's surface, sebum

C.       Skin-pH-Meter PH 905: pH-measurement

D.       Mexameter® MX 18: Melanin & erythema

E.       Tewameter® TM 300: Transepidermal water loss measurement

F.        Indentometer IDM 800: Mech. Properties

G.       Elastometer EM 25: Viscoelasticity by suction

H.       Skin-Thermometer ST 500: Body heat

I.         Skin Glossymeter GL 200: Appearance of skin and hair gloss

J.         Skin-Colorimeter CL 400: Skin and hair colors

Frictiometer FR 700 

Friction readings on the skin using the Frictiometer FR 700.

The MPA Systems (Multi Probe Adapter) It's modular to use the Multi Probe Adapter System. It consists of probes and a basic device.

·       The user selects a basic device that meets his needs. The probes are digital containing all calibration data. Therefore, they can be connected to any of them.

·       The probes provide a high degree of flexibility and stability and can be easily serviced.

·       Operation with the overall MPA CT plus software for all devices and probes (with cables).

·       The accuracy of the probes can always be checked with a check calibration function.

·       The measurements include the room temperature and relative humidity from the sensor RTH 100.

·       The perfect solution for efficacy testing, claim support, various scientific investigations, and field trials.

·       The Multi Probe Adapter Systems can feature up to 10 different probes and are connected directly to the software (no display on the device).

·       Measurement system that is ideal for your needs and can grow as you go.

·       The brand-new, cutting-edge programme MPA CT plus is used to operate the MPA systems.

·       The measurements are saved along with the information from the RHT ambient condition sensor.

·       The system may be well-suited through all upcoming cutometer probes.

Available models:

·       With the exception of the Cutometer®, the Multi Probe Adapter MPA 6 supports up to five probes and has an integrated Sebumeter®.

·       A built-in Sebumeter® and the possibility to connect any probes with an external power source are features of the Multi Probe Adapter MPA 10 (up to 9, excluding Cutometer®).

·       The Cutometer® dual MPA 580 has a built-in Sebumeter® and the capacity to connect up to four additional C+K-probes, and it uses a vacuum pump inside the device to induce suction in order to measure the viscoelasticity of the skin.

·       The tool comes with one Cutometer® probe (2 mm standard opening), extras, and software. Another alternative is to connect and use more than one Cutometer® probe simultaneously. Connect any two in MPA 2 (aside from the Frictiometer and Cutometer®), there is no need for an additional power source; simply connect the device with the system through USB. (Does et al. 2017)

A.    Corneometer® CM 825

The most popular instrument that measures skin hydration in the world is Corneometer® CM 825 Over the course of 35 years. The Corneometer® has made it possible to consistently and precisely determine the degree of moisture on the skin's surface (stratum corneum). The fact that the term "corneometry" is used in so many scientific publications and that measures of skin moisture depend on one another is proof of this. Other hydration measurement devices on the market are always compared to the Corneometer® standard to determine their accuracy. (Anon 2017)

Fig 2: Corneometer® CM 825(Anon n.d.-l)

The Corneometer indicates hydration of the superficial layers of the skin (stratum corneum) via measurement of skin dielectric properties. The measurements are performed by the application of a probe to the skin surface. Upon contact, an electric field passes through the stratum corneum and the dielectric constant is obtained. The amount of skin hydration is exactly proportional to the value of the dielectric constant (in arbitrary units). The Corneometer has given the most popular and reliable method for calculating the degree of moisture of skin surface for more than 35 years (stratum corneum). The numerous scientific publications that use the terms "corneometry" and "skin hydration measures" interchangeably serve as evidence for this. Other hydration measurement devices on the market are always compared to the Corneometer standard to determine their accuracy. The measuring of skin moisture with corneometry is a common technique. It measures the relative permittivity of the upper skin layers using a capacitive sensor. The measured value serves as a metric because these depend on the skin's level of moisture level of the skin. The German trademark Corneometer is where the name corneometry originates. Under this name, the first commercial skin hydration measurement device was released in 1979.

Fig 3: Hydration level detected on the stratum cornea (outermost skin layer) (Skin Hydration Measurement by Dr. Jonathan Crowther Via SpecialChem • Skinob , Cosmetic Testing, n.d.)

Measurement principle

A capacitance measurement of a dielectric material, in this case skin, is the foundation of the Corneometer measurement. The dielectric constant of the skin is measured using fringing field capacitance sensors. Skin's dielectric constant will alter depending on how much water is present. This enables the precision measuring capacitor to detect any changes in skin moisture. These variations in the stratum corneum's water content are transformed into arbitrary hydration units. On the probe head there is a fine piece of glass to ensure that only the capacitance changes due to water content are identified. Even small changes in water can be detected.  The measurement time is short at only 1 second minimizing occlusion effects. The stratum Corneum, at a depth of 10–20 m, prevents deeper layers of skin from influencing the measurement.

Application areas

      I.     Ideal for product development, supporting claims, and efficacy testing

    II.     Can be utilized for unbiased clinical evaluation can be used to keep track of treatments provide details on the course of treatment

  III.     For use in medical surveys Various scientific applications that involve evaluating hydration

Benefits of a Corneometer

1.     To avoid blockage, the probe enables very quick measurement (1 s).

2.     Optionally, measurements over a longer time span might be done continuously ("dynamic occlusion").

3.     Due to capacitance measurement, substances on the skin (such as salts or product residues from topically applied goods) have very little impact.

4.     To avoid contamination, measurement depth is quite shallow (10–20 m of the stratum corneum).

5.     For simple handling and measurement on all body sites, the probe is compact and lightweight (e.g., lips, etc.). The probe head's spring keeps the pressure on the skin constant for precise, repeatable results. It is simple to evaluate the Corneometer® probe's accuracy and the scatter field's penetration depth at any moment.

6.     It takes little time to clean the probe head after each measurement. With a wide spectrum of investigations, "corneometry" is widely recognised.

7.     The condition of the skin of the astronauts aboard the International Space Station was evaluated using the Corneometer® (ISS). The most recent recommendation for measuring skin water by the experts of EEMCO (European group on efficacy measurement and assessment of cosmetics and other products) is to use the Corneometer®. (Skin Research & Technology, 2018, 24, p. 351-358).

8.     The Corneometer CM 825 is existing as an individual instrument, derma section SSC 3, connectable to the MPA systems, or as a wireless probe.

Available formats

1.      Multiprobe Adapter System

The Corneometer CM 825 probe can be plugged in to all of the computer driven MPA devices (MPA 2, MPA 6, MPA 10 & Cutometer dual MPA 580)

2.      Multi Display Device Mdd 4

The Corneometer CM 825 is available as a stand-alone device through the MDD 4. Supplied with a room condition sensor may be likely to add a further two measurements. In addition to the color screen for displaying results the MDD 4 can be connected to a computer and measurements recorded using the MPA software.

3.      Wireless Probe

Radio waves are used to transmit measurements to the diminutive RR 200 receiver unit, which is connected via a USB port to the computer. The values can be transmitted over a 5–10 m distance. The values are collected using special MPA Wireless software. The probes are battery operate.

Technical Information

Length: 11 cm, Weight: approx 41g,

Measuring surface: 49mm2,

Measuring principle: capacitance, Measurement frequency: 0.9-1.2 MHz, Accuracy: ±3% Technical changes may be made without prior notice.

Benefits

1)     Repeatable and since 1980,

2)     Precise measurements of skin hydration.

3)     Brief measurement period

4)     Constant pressure for repeatable measurements that are accurate and unaffected by skin.

5)     Taking measures at each skin spot makes individual and continuous measurements possible not frequently, intricately, or laboriously require calibrating Data on calibration kept in the probe Check To ensure the accuracy of measurements, test the calibration.

6)      A shallow depth measurement

7)     The moisture content of the stratum corneum affects a number of skin characteristics, including its mechanical qualities and barrier function.

As a result, measuring hydration is now among the most significant and widely utilised metrics. Other hydration instruments are constantly evaluated and contrasted with the Corneometer®, which is the most popular hydration assessment device in the world. High-quality electronics in the probe ensure temperature stability in addition to preventing fluctuations from interfering with the measurement. The probe's light weight and small measurement area (49mm2) make it simple to use measurements across the entire body.

Methods

The experimental apparatus included a combination of cellulose and saline to simulate the SC and polyethylene foil to simulate the underlying skin layers that contain a lot of water. Following the application of three different skin formulations, base, base plus salt (2 wt% NaCl), and base plus salt and glycerine (5 wt%), the hydration of the SC of the volar forearm was assessed in eight healthy volunteers using the Moisture Meter SC-2 and Corneometer CM 825. In the sorption-desorption test, a drop of water was applied to the skin, and both instruments monitored the skin's dehydration for two minutes.

SM 815 Sebumeter

Sebaceous gland secretions, keratinous layer fat, and sweat remnants all contribute to the heterogeneous components of sebum. Glycerides, free fatty acids, wax esters, squalene, cholesterol esters, and cholesterol are only a few of the lipids that make up sebum, which is a complex and changeable mixture. There are various kinds of instruments available for measuring sebum production. Sebumeter® provides the furthermost prevalent technique for reliably and accurately determining the sebum level for 35 years and plus of the skin's surface, the scalp, and the hair. The numerous occurrences of these terms in scientific literature serve as evidence for this. Sebum measurements and "sebumetry" go hand in hand.(S 2022)

Fig 4: Measuring sebum on skin

Measurement of sebum 

Lipids are synthesized at a constant rate in sebaceous gland and secreted onto the skin surface an average of eight days after synthesis. Therefore, by measuring the sebum content of a skin specimen with a known surface area, it should be possible to determine the sebum production rate that had been occurring in vivo. According to a study on men, the average rate of scalp sebum production is 1.45 mg.

Fig 5: Demonstrates the sebum production averages from human skin.

Measurement Principle

Grease spot photometry is the foundation for the measurement. The skin or hair comes into contact with the Sebumeter SM 815 mat tape. Depending on the amount of sebum on the measurement area's surface, it turns translucent. A photocell then tests the device's transparency and aperture after inserting the tape inside. Transmission is an example of a light Sebum content.                    

Fig 6: Optical diagram of sebumeter

The Probe (Cartridge)

A 64 mm2 measuring section of the mat tape is visible through the measuring head of the cartridge. For a measurement the tape is moved forward by a trigger at the side of the cartridge to expose a new section of tape. The used tape is rewound inside the cartridge. 400 measurements can be made with one cartridge. How much of the tape is still unutilized is shown on the trigger by the scale from 1-0.

For hygienic reasons, the cartridge is simply replaced when it runs out.

Positive aspects of the Sebumeter

§  The unique tape solely reacts to the content of skin sebum and is independent of water.

§  It enables very quick and simple measurement to prevent occlusion.

§  A zero calibration before each measurement provides highest accuracy.

§  For simple handling and measurement on all body locations, the probe is compact and light.

§  Precision and repeatability are made possible by the cartridge's spring, which maintains consistent pressure on the skin.

§  It is simple to check the device's accuracy at any time using a particular test tool with a predetermined value.

Fig 7: Cartridge on head

Fig 8: Cartridge on cheek

Application Areas

The sebum content is important in several application areas, including:

§  For all types of cosmetic and pharmaceutical products, claim support and efficacy testing are crucial (especially cleansers, anti-acne products, shampoos and hair care, products for oily skin).

§  Typical claims (examples) supported by the Sebumeter include protection from oily skin, hair, and scalp, cleaning/purifying, against impurities, oil restoring, anti-dandruff, anti-acne,  calming, nourishing, opulent, balancing, normalising, safeguarding, and pore activity  decreasing, among other things.

§  It is beneficial in a typical in dermatological basic research in humans and animals.

Fig 9: Sebumeter basic efficacy testing face wash

Fig 10: Sebumeter basic device in cosmetic research

Technical Data:

A.    Cartridge only

Dimensions: 8.5 x 11.3 x 2.3 cm, Measuring surface: 64 mm², Weight: 65 g,

Units: Sebumeter® units from 0-350 (approximated to μg/cm2 in a certain range), measurement uncertainty: ± 5%

A single cartridge provides about 400–450 measurements. Expired cartridges must be replaced.

B.    Skin-pH-Meter PH 905

Skin-pH-Meter PH 905 used to measure the pH of the skin and scalp. For quickly, easily, and affordably measuring the pH on the scalp or skin surface, use the Skin-pH-Meter PH 905 device. The H+ ion and one housing each include a sensitive electrode and an extra reference electrode, which are measured using a high-quality combination electrode. It is connected to the measurement electronics found on a probe handle.(Courage+Khazaka electronic GmbH 2022)

Fig 11: Measurement of skin pH(Anon n.d.-e, Anon n.d.-h)

C.    Mexameter® MX 18

The Mexameter® MX 18 is a very simple, quick, and affordable tool for measuring erythema. The two substances primarily responsible for the skin's colour, melanin and reflecting haemoglobin (erythema). Changes in skin tone are relevant in a wide range of application areas. The instrument is well-known and widely used in scientific research. It is essential for supporting efficacy claims and testing for cosmetics and pharmaceutics.

 A Mexameter is a tool that helps in measuring amount of melanin or erythemal that is present in the person’s stratum corneum who being tested. This help in understanding If someone is afflicted with from deficiency or excess of these two components. The measurements are performed by the application of a probe to the skin surface. The probe has a 5 mm aperture that emits radiations. These radiations are reflected by the skin and captured back by the same probe.(Anon 2022b). The results are expressed as index value for each parameter (melanic index and erythematic index) in arbitrary units on a scale from 0 to 999. 

Fig 12: Mexameter® MX 18 (Anon n.d.-c)

Measurement principle

Absorption/reflection is the foundation of the measurement. The Mexameter® MX 18 probe emits three distinct light wavelengths. The receiver measures the light reflected by the outermost layer. After the light emitted amount is determined, the amount of on the skin, light absorption can be calculated. Two distinct wavelengths are used to measure the melanin (red: 660 nm and near infrared: 880 nm) was chosen to match various pigment absorption rates. In the t wo distinct wavelengths are used to measure erythema: green (568 nm) and red (660 nm), which corresponds to the haemoglobin spectral absorption peak, and to prevent other colours have an impact (e. g. bilirubin).

Benefits

·        Measuring erythema and melanin in a reliable and accurate manner

·        Extremely rapid measurement time

·        The constant pressure provided by spring has no impact on the skin.

·        Low weight provides easy handling

·        Do not need regular, complex and time-consuming recalibration

·        Data on calibration kept in the probe

·        Verify calibration to ensure measurement accuracy.

Fields of Applications

Skin colour are of interest in various fields. Many international scientific studies demonstrate its benefits in all important dermatological basic research in humans and animals and cosmetic application fields.

1.      It is indispensable in efficacy testing and claim support for cosmetics and pharmaceuticals 

2.      Typical claims (examples) substantiated with the Mexameter^®: sun protecting, whitening/brightening, skin tone correcting, concealing, soothing, micro circulation increasing, vitalising, anti-allergic, anti-irritation, safe, for sensitive skin, anti-pollution, improves healing, anti-aging, against dark-spots/age-spots/dark-circles, anti-photosensitive and many more.

3.      In occupational health the skin irritation (erythema value) is of special interest to show the necessity of skin protection measures

4.      Ideal for product development, supporting claims, and efficacy testing

5.      It is used for patch testing, allergy testing, and objective clinical assessment.

6.      Used keep track of treatments

7.      Measurement of melanoma and scar tissue

8.      Suitable for medical surveys

9.      Assessing melanin and erythema in a range of research applications

Benefits of Mexameter®

§  Measurement is rapid and easy (1 second for the results: melanin index and erythema index).

§  Continuous measurements over a longer time span are optional.

§  The highly sensitive measurement provides results for melanin and erythema on a wide scale (0-999), making even the smallest variations in colour traceable.

§  It is lightweight and tiny enough to be handled easily and measured on all body regions.

§  A spring within consistent pressure from the probe head on the skin enables precise, repeatable measurements.

§  The accuracy of the Mexamete^r® probe easily checked at any time.

§  The probe head can easily be cleaned after each measurement.

§  Worldwide established and used in many scientific studies.

Technical Data

Probe only:

Dimensions: 13 cm x 2.4 cm Ø, 

Measuring surface: Ø 5 mm ≈ 19.6 mm²,

 Cable length: approx. 1.3 m,

 Weight: 85 g (incl. cable)

Measurement principle: absorption/reflection,

Nominal wavelengths: 3 colour measuring system

green: λ peak = 568 nm,

red: λ peak = 660 nm,

near infrared: λ peak = 880 nm,

 Units: arbitrary Mexameter^® units (0-999 for melanin and erythema), 

Measurement time: 1 s, 

Measurement uncertainty: ± 5%

B.    Tewameter® TM 300

Measurement of Transepidermal Water Loss and Skin Barrier Function

The Tewameter® TM 300 (the predecessor to the Tewameter® TM Hex) is the most widely used measuring tool for the estimation of Transepidermal Water Loss because of its "open chamber" principle(TEWL). This is a crucial variable for determining how well the water barrier function of the skin and a fundamental measurement for all applications. Even the slightest damage in the skin water barrier can be determined at an early stage.(Anon n.d.-j)

Fig 13: Tewameter TM 300 probe(Anon n.d.-j)

What Does It Measure?

The Tewameter® TM 300 is the most widely used instrument for monitoring transepidermal water loss (TEWL). The evaluation of the skin's barrier function is based on this factor the most.

The most used tool for monitoring transepidermal water loss is the Tewameter® TM 300. (TEWL). This information is essential for figuring out how efficient the skin is as a barrier. Due to its "open chamber" approach, the Tewameter® TM 300 (the Tewameter® TM's predecessor Hex) is the measurement device that is used the most frequently worldwide (TEWL).

This is a fundamental measurement used in all kinds of applications and a crucial parameter for assessing the skin's ability to act as a water barrier. Early detection of even the smallest skin water damage was possible.

Measurement Theory

Water from the skin always evaporates to some extent as part of natural skin metabolism. However, the water loss will accelerate the moment the skin's barrier function is even slightly compromised (even with the smallest damages invisible to the human eye). As a result, this assessment serves as the basis for all cosmetic and dermatological research. The two sets of sensors inside the hollow cylinder (temperature and relative humidity) allow the Tewameter® probe to indirectly measure the density gradient of skin water evaporation.

This is an “open chamber” measurement. The TEWL can only be constantly assessed using this method without changing its microenvironment. In g/h/m², the measured values represent the evaporation rate.

A = surface [m²]

m = water transported [g]

t = time [h]

D = diffusion constant [= 0.0877 g/m(h(mmHg))]

p = vapor pressure of the atmosphere [mm Hg]

x = distance from skin surface to point of measurement [m]

Fields of Application

·       Indispensable in formulation, efficacy testing and claim support for cosmetics and pharmaceuticals, regarding improvement of the skin barrier function.

·       Safety tests for products as even slight deficiencies in the skin barrier can be detected.

·       Dermatological basic research.

·       Studies on sweat (antiperspirant efficacy testing).

·       Measures used in occupational health education to inform people about the need for

·       products that protect the skin.

·       Zoology and veterinary medicine.

·       Also, for the textile, food, packaging and paper/ tissue industry, the measurement is of interest.

Advantages

·       The open chamber measurement is the only method to assess the TEWL continuously, which is necessary for most applications, without influencing the skin surface.

·       Numerous studies available.

·       A stable measurement is achieved quickly; the next measurement can be done without waiting time.

·       The small size of the probe head reduces the impact of air turbulence inside the probe.

·       Its light weight ensures easy handling and has no impact on the skin's structure.

·       Easy check calibration with a small chamber.

·       Offset of probe by the user possible for compensation of “aging effects “of the sensor.

·       Special calculations i.e., Skin Surface Water Loss (the skin ‘s water holding capacity after occlusion).

·       Available as a standalone device (MDD) and wireless probe for C+K MPA-systems (operation with MPA Wireless software).

Skin temperature is 30°C or higher, while the sensors of the probe typically operate at room temperature (20–22°C). As the amount of evaporating water measured with the device is extremely small (healthy skin 8-15 g/h/m² → 0.000001333 - 0.00000025 g/minute/cm²), the sensors inside the probe should reach skin temperature to measure this small amount exactly and stable. The Probe Heater PR 100 continuously raises the probe head's temperature to a temperature getting very quickly accurate and stable and being close to skin temperature results.

Special Accessories for Tewameter® TM 300

Disinfectable steel rings are available when measuring on special surfaces. They can be mounted on the measuring head and after the measurement taken off the probe and be cleaned.

Technical Data

Cable probe only:
Dimensions: Measuring Chamber: Height: 2 cm, Ø 1 cm, Probe: Length 17 cm, Cable length: approx. 1.3 m, Weight: 75 g (incl. cable), Resolution: Humidity: ± 0.01 % RH, Temp.: ± 0.01 °C, TEWL: 0.1 g/h/m²

Operating conditions: T: 10-40° C, RH: 30-70 % RH

Specified measurement conditions: 10° C to 40° C and TEWL-values lower than 70 g/h/m²
TEWL: ± 10 % of the measured value plus ± 0.8 g/h/m² for RH ≥ 30 %; ± 1.3 g/h/m² for RH ≤ 30%
Temperature (T): ± 0.5 °C
Rel. humidity (RH): ± 1.5 % for RH between 30 % and 90 %, ± 2.5 % for RH values outside this range

Probe Heater PR 100: Power supply: external 100-240 VAC, 47-63 Hz, DC 12V/4A, Dimensions: 10 x 11 x 10.5 cm, Weight: 470 g

Other Available TEWL probes:

1.     Tewameter^® TM Hex: 

The ultimative TEWL measurement with one head (NEW).  The Tewameter® TM Hex assesses the Transepidermal Water Loss (TEWL essential component for the evaluation of the performing as a water barrier, the skin, with a revolutionary accuracy and reproducibility. 30 sensors inside the probe “see” temperature and relative humidity like a camera. The high amount of data allows the user not only to highly accurately measure inside the probe but can show results also for the areas right outside the probe, namely skin surface and ambience above the probe.  (Anon 2021)

Fig 14: Tewameter® TM Hex

2.     Tewameter^® TM Nano: Ultra-Small TEWL Measurement Probe for Special Skin Sites

With its exceptional small measuring chamber (only 2 mm Ø), the Tewameter® TM Nano allows to measure the Transepidermal Waterloss (TEWL) in g/h/m² on small, or difficult to reach sites, e.g., nails, scalp with hair, lips, etc.  (Anon 2021)

Fig 15: Tewameter® TM Nano

3.     Tewameter^® Triple TM 330T: TEWL measurement probe with three flexible measurement heads. Tewameter® Triple TM 330T The probe follows the worldwide acknowledged open chamber measurement of the Tewameter®. It does so by using two sets of sensors (temperature and relative humidity) inside the hollow cylinder to indirectly measure the gradient of water evaporation from the skin. A microprocessor analyses the values. It is very suitable device to reduce the measuring time as with its three probe heads it supplies three measurements at the same time. (Anon 2021)

Fig 16: Tewameter® Triple TM 330T

4.     Invitro Tewameter^® VT 310: TEWL measurement directly on Franz cells. A special probe for the measurement of the TEWL, perfectly suited to fit on a Franz cell. The probe emulates completely the upper part (donor chamber, standard is 15 mm Ø, other sizes on request). A convenient way to study skin permeability and dermal absorption necessary for safety & efficacy testing.(Anon 2021)

Fig 17: Invitro Tewameter^® VT 310

5.     Tewitro^® TW 24:  TEWL measurement on up to 24 cultured skin wells simultaneously. The Tewitro^® TW 24 is the only device to measure the water evaporation from cultured tissue sets (wells in a plate with medium) in up to 24 wells simultaneously with the worldwide most used “open chamber” measurement of the Tewameter^®.

Fig 18: Tewitro^® TW 24

C.    Intendometer IDM 800

 Assessing Skin Mechanical Skin Properties from a Different Angle

The Indentometer IDM 800 is a quick, easy and economical tool to look at the skin softness/stiffness. Probes with 3 different pin diameters (2, 3 and 5 mm Ø) are available, suitable for various skin sites. The smaller the diameter, the deeper the pin goes into the skin when using the same force as the contact area with the skin is smaller. The Indentometer is connectable to the MPA systems.(Anon n.d.-k)

Fig 19: Intendometer IDM 800 (Anon n.d.-b, Anon n.d.-k)

D.    Skin-Glossymeter GL 200

Measuring Gloss on Skin, lips and Hair

When evaluating the effectiveness of skin care, hair care, and decorative cosmetics, gloss measurement is crucial (lipsticks, make-up, etc.). Skin and hair should have a luminous, natural sheen without looking greasy.(Anon 2022a)

Fig 20:Skin-Glossymeter GL 200 (Anon n.d.-i)

E.     Skin-Colorimeter CL 400

An Economical Way to Look at Skin & Hair Colour

The colour of the skin is specifically measured by the Colorimeter CL 400.It can be applied to hair as well. Coordinates in the colour space are used to express measurement values.

(Or as RGB - red/green/blue) space L*a*b*(Anon n.d.-f)

Fig 21: Skin-Colorimeter CL 400 (Anon n.d.-f)

F.     Skin-Thermometer ST 500

Microcirculation and Skin Temperature Evaluation A quick, simple, and affordable tool for measuring skin temperature—which is a sign of the microcirculation of the skin—is the Skin-Thermometer ST 500.

Fig 22: Skin-Thermometer ST 500 (Anon n.d.-d)

G.   Elastometer EM 25

Determination of Skin Aging with Elasticity Measurement EM 25

The elasticity measurement probe with display and interpretation chart that is most frequently used worldwide. The biological skin age (elasticity of the skin) is measured quickly and easily by (Skin's resistance/firmness compared to its capacity to return to its initial state) suction position). The outcome is presented as a percentage, and a chart links the measurement to the age of a person.

Fig 23: Elastometer EM 25 (Anon n.d.-a)

PRINCIPLE-

The principle is based on a mechanical deformation of the skin via the suction method. A negative pressure is created in the device and the skin is drawn into the 2 mm aperture of the probe. The device develops a negative pressure, which draws the skin into the probe's 2 mm aperture. The skin is drawn into the probe's aperture by the device's pressure, which is then released after a predetermined amount of time.

Fig 24: Suction hand and released hand

A non-contact optical measuring system inside the probe uses the Cutometer principle to determine the penetration depth. The components of this optical measuring system are a light source, a light receptor, and a light is projected from the transmitter to the receptor by two prisms facing each other. The depth of the skin's penetration affects light intensity. The skin's resilience to the firmness of the negative pressure and its capacity to revert to its initial position(elasticity) are shown in real-time as curves (penetration depth in mm/time). The different forces of elastin and collagen in the skin are what give human skin its typical shape of a curve. Elastin is in charge of the Cutometer collagen vs elastin-flexibility of the skin whereas collagen’s main task is to keep the skin in shape.

The first, very straight part of the curve is shaped by the proportion of elastin in the skin as it easy to displace and very flexible. Collagen has taken over when skin starts to "creep" inside the probe. It is more durable and better able to withstand mechanical force. As soon as the device's pressure has stopped, the collagen begins to bring skin back to life returning to its initial form. Consequently, in youthful skin with new collagen, the skin immediately compared to older skin, it reverts to its original position more closely. Finally, the eventual Elastin ensures that the skin heals completely.

Fig 25:  Elastometer typical curve collagen vs elastin

Measurement Parameters

The user can adjust the MPA CTplus software's settings to suit various applications (such as suction time, relaxation time, pressure/pressure rate, repetitions, etc.). The programme enables the calculation of numerous fascinating parameters from variousthe suction and recovery portions of the measurement curve. The majority of measurements in the literature have been made using mode 1 (full suction then through total relaxation). Here a short overview:

R-Parameters –

·       R0: Uf firmness/pliability mm (amplitude at the end of the suction phase)

·       R1/R4: Skin's capacity to return to its original state (remaining deformation in mm after recovery)

·       R2: (resistance to mechanical force versus capacity for recovery) viscoelasticity in percent

·       R3/R9/R10: Fatigue effects in mm are evident for continuous suction/recovery circles.

·       R5: net elasticity in %: Ur/Ue = elastic part of the suction phase \svs.\simmediate recovery during relaxation phase

·       R6: Uv/Ue Portion of the Curve's Viscoelasticity During the Suction Phase in %

·       R7: Ur/Uf ratio of the instantaneous recovery to the amplitude following suction in%

·       R8: Ua Total recovery in millimetres following the loss of pressure

Area Parameters (F):

·       F1: The region above the curve when suction is occurring. There is less area the more elastic the material.

·       F2/F3/F4: "Skin Fatigue" 

Fig 26: Area parameters

Q-Parameters:

The scientist Di Qu (Senior Research Scientist, R&D Skin Care, Amway Corporation, Ada, Michigan, USA) created a set of parameters that display intriguing correlations. The relationship between skin age and the curves' elastic and viscous recovery

·       Q0: Area of maximum recovery

·       Q1: Total recovery (overall elasticity) - (QE + QR)/Q0

·       Q2: Elastic recovery - QE / Q0

·       Q3: Viscoelastic recovery - QR / Q0

Fig 27: Age and the elastic and viscous recovery of the curves are correlated.

*From: D. Qu et al., Correlating Age and Quantifying Product Efficacy on Human Skin Using Novel Viscoelastic Parameters.

Technical Data

Device: Dimensions: 24 x 20 x 7 cm, Weight: approx. 2.2 kg, External power supply: 100-240 VAC/12VDC.

CONCLUSION

This review attempts to demonstrate the convenience that some basic or sophisticated techniques often already applied to other purposes could provide for the quality monitoring of cosmetic products for dermatological use in women. Due to the significant contribution that the C+K probe devices may make to the cosmetic industry, they have drawn attention. The C+K probe family is now being used in a completely new way thanks to this updated software, which also includes several useful new capabilities. The technique most frequently used worldwide to measure capacitance-based skin surface moisture, oiliness, activity of the sebum glands, redness and melanin measurements are useful for determining skin sensitivity, elasticity and biological age of the skin an important tool for all kinds of skin and body care goods. One second is all it takes to perform the quick and simple measurement. Most of the measurement is done using a probe devices with an integrated measurement probe. Cutometer® dual MPA 580 has an integrated multi probe adapter system and can connect up to eleven C+K-probes. The devices are claimed to support cosmetics, pharmaceuticals, raw materials, household/personal care products, detergents, as well as food and food supplements. They are used as standard instruments in efficacy testing across the globe. Women have softer skin as compared to men. Thus many scientists provide new discoveries in dermatology and cosmetology.

Acknowledgment

We would like to express our sincere gratitude to the head of the Phyto-formulation, Cosmetic, and Nano Drug Laboratory at the University Institute of Pharmacy, Pt. Ravishankar Shukla University in Raipur, Chhattisgarh, for their efforts in creating this manuscript.

Conflicts of Interest

The authors declare no conflict of interest related to the submission of this manuscript and the manuscript is approved for publication by all author.

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