ANTI-AGEING SUBJECT 1 SUBJECT 2 SUBJECT 3 SUBJECT 6 SUBJECT 14
63
Figure 5: Irradiation sites on the forearm in method 2 Note: Both control group (upper panel) & active group (lower panel) were UV-irradiated. Control group is w/o SG-peptide. Images were taken on D15
Photographs of skin treated with the SG-
peptide, taken on the forearm after 15 days, are shown (Figure 5) with darker tanned spots in the middle representing the UV-irradiated part of the skin. For a better visualisation of this tanning effect, we then transferred the data, as delta ITA° values, to a digitally created average facial image. Instead of using the mean delta ITA°
values from the complete study panel, for a more impressive visualisation we used the ITA° values from two selected subjects (#3 and 6) who showed a very positive individual tanning reaction (Figure 6a-b). In the split face views, the left side shows the tanning level taken from forearm data after UV irradiation only, and the right side shows the tanning level taken from forearm data after UV irradiation and treatment with the SG-peptide. The prolonged tanning effect that can be seen seven days post treatment with SG-peptide (Day 22) is noticeable.
Discussion In this paper, we describe two methods to digitally simulate tanning reactions on the forearm on the face. Irradiation with solar light, specifically in the UV or blue light range, causes readily visible changes in skin colour. In addition, it can induce erythema and is potentially harmful with respect to cellular damage, such as DNA mutations or creation of reactive oxygen species34,35
. Because of this, irradiation experiments
are often performed on surrogate body sites such as the back or the forearms, where the harmful effects still persist, but visible colour changes like pigmentation or reddening cannot readily be seen by others. Such irradiation may also cause a stinging or burning sensation, and this is likewise better accepted on areas such as the back or forearm instead of the face. Moreover, UVR is harmful to the eyes, which is another safety concern for facial irradiation.
www.personalcaremagazine.com Our methods provide a way to simulate
facial solar irradiation, and the resulting visible pigmentation and colour changes, either on images of real faces or images of 3D artificial faces. Although they involve a mathematical transfer of colour, these methods give an idea of how colour changes induced on areas such as the forearm would look on the face without irradiating the face. This method offers the advantage of simulating such pigmentation reactions on the whole face, whereas irradiation experiments are normally only performed on small areas and would therefore not show changes on a larger area. In addition, only small test areas are necessary on surrogate body sites. This makes it possible to test several different conditions per subject, making studies more time- and cost-efficient. One limitation of these methods is that
they show uniform colour changes over the whole face based on measurements on a single spot, which may not accurately represent real world colour changes. In fact, we have shown in other studies that changes in skin tone in Asian volunteers are different on different areas of the face32
true for other facial skin parameters such as hydration and water content36,37
. This is also .
Spatial differences in facial colour change
may be due to different facial characteristics such as thickness, sebum content or the distribution of melanocytes. In addition, tanning in forearm skin is not necessarily the same as in facial skin, due to differences in skin thickness or initial photodamage. Along those lines, light of specific
wavelengths may not have the same impact on forearm and on face due to for example non-photoexposed vs. photoexposed skin. As far as irradiation is concerned, differences may also be due to the three-dimensional topography of the face which leads to variation in irradiation intensity due to a steeper or flatter irradiation angle.
Our first method partially resolves this limitation, because we take the calculated colour of every pixel of the facial image as a starting point. This takes account of all differences in skin colour over the whole face, at least at the beginning (Figure 2). Only afterwards, when adjusting to forearm colour and calculating delta values between treatments and timepoints, is the colour shifted as a whole (Figures 2 & 3). In method 2, we transfer forearm colour to
a 3D-image of a simulation of a typical face which is composed of several individual face images. Average facial images are computed from several images, which are registered and averaged32
. Here, any irregularities on the face
disappear and the colour looks more even (Figure 6a-b). The more even look and the homogenous skin
tone achieved with method 2 is very useful for visualising treatment effects as they enable slight differences in colour variation to be seen more easily, whereas method 1 preserves the more natural and individual look of the skin’s colour. Another important advantage of both methods is the possibility for better standardisation of test conditions. As the tanning effect of blue light and the SG-peptide are also triggered by sunlight, the forearm skin could easily be protected using a long- sleeved shirt. However, such standardised light conditions would not have been applicable in a direct facial study. In summary, we provide here two new methods with which we can simulate pigmentation reactions, induced by solar light irradiation, on the forearms.
Acknowledgements We are grateful to the volunteers for their participation in the clinical studies. In addition, we would like to thank our colleagues at DSM Nutritional Products and Newtone Technologies for productive discussions throughout this project
PC March 2022 PERSONAL CARE
30 PPM FORMULATED TANNING PEPTIDE
CONTROL GROUP
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