68 SUN CARE
values of the irradiances across the spectral ranges were E (UVB = 280 – 320) = 23.5 W/m2 W/m2
and E (UVA = 320 – 400 nm) = 180 . An increase in UV doses was
achieved by increasing irradiation times. The emitting intensity was controlled
before each measurement. A cut-off filter of 320 nm (ITOS W-NG-320, Schott) was used to obtain UV A radiation only. ESR measurements were performed with a highly sensitive benchtop MiniScope (MS 5000) electron spin resonance spectrometer, supplied by Magnettech GmbH Berlin, Germany.2
Clinical study
The test subjects, all sensitive to A. aestivalis, were irradiated using UV A radiation only, on 5 successive days, using a solar simulator (SOL 5, Hönle AG, Germany). The irradiation dose was 20 J/cm2
, far below the erythema threshold.
The test formulations, as well as the positive and negative control, were applied to the décolletage area 10 minutes prior to the irradiation. The skin reactions were evaluated directly after each irradiation and again after 24 hours, prior to the next irradiation dose. A standard sunscreen gel (SPF 30) which never induced a skin reaction in sensitive subjects served as a negative control and a sunscreen formulation was used as a positive control, which triggered A. aestivalis in disposed subjects.
Results
An example of RP data is given in Figure 1: A cosmetic formulation was spiked with natural oils or perfume oils (PO). The almond oil showed higher radical generation compared to olive oil, probably due to differences in the fatty acid composition and the oxidation grade. The two perfume oils showed very different reactions: PO “A” showed very low radical generation (RP = 6.6%), whereas PO “B” showed a strong radical generation under UV (RP = 63.9%). Sensorial properties had not changed. The added perfume oils differed in terms of terpene composition, oxidation state, and particularly in with regards to the content of hydroperoxide- terpenes, which was most likely to be the reason for their different behaviours. For the two sunscreen formulations that
were produced, both with an SPF of 30 and the same UVA/UVB ratio, only the UV filter composition differed (see Table 1). Formulation 12-1 contained only photostable UV filters, whereas Formulation 12-2 also contained photo-unstable filters. The Radical Potential (RP) of both formulations was detected, using the full spectrum of UV light (280–400 nm), and the UV A region of the spectrum (320–400 nm) only, since A. aestivalis is reported to be
PERSONAL CARE EUROPE
n negative control n Positive control n 12-1 (low RP) n 12-1 (high RP)
0.6 0.5 0.4 0.3 0.2 0.1 0
0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 days of treatment
Figure 2: Score evaluation of the clinical study.
induced mainly via UV A radiation. Formulation 12-1 did not induce free radicals, whereas Formulation 12-2 showed a high degree of radical generation, both under full-spectrum UV and UV A radiation (45.3% and 21.9%, respectively) (see Table 2). The two sunscreens 12-1 and 12-2 were tested with regards to their capacity to induce skin reactions, i.e. A. aestivalis in sensitive subjects:
Positive control The most intensive reactions were observed after the positive control was applied. This internal standard served as a control of the inducibility of skin reactions in the selected test subjects.
Negative control In the test areas treated with the negative control, a standard sunscreen gel- formulation, no skin reactions were observed in any of the subjects (reference for positive and negative control: confidential information – DermaTronnier).
12-1
In the test areas treated with the sunscreen Formula 12-1, during the 5-day treatment, no skin reactions could be observed in any of the 6 subjects. The formula offered complete protection against skin reactions.
12-2
The sunscreen Formula 12-2 provoked skin reactions classified under A. aestivalis in 5 out of 6 subjects. Subject number 4 showed only slight symptoms, which already
occurred after the third exposition day. Subject numbers 1, 5, and 6 showed light to distinct reactions during the exposition time, so that after the third and fourth day no further irradiation and treatment could be applied for ethical reasons. Subject number 3 already displayed severe skin reactions after the second treatment day, so no further irradiation could be applied here after day 4. The results in Table 3 were quantified using a score system, which is illustrated in Figure 2.
Discussion Two sunscreen formulas were investigated. Both contained organic UV filters only, both with the same SPF (SPF 30) and comparable protection in the UV A spectral range. Very different RP values (levels of UV-induced free radicals) and completely different skin reactivity were obtained where an excellent correlation between the in vitro parameter (RP) and the clinical symptoms could be shown.
Despite the relatively low number of subjects, this result yielded an excellent correlation between the in vitro parameter (RP) and the clinical symptoms, corroborating the hypothesis of involvement of free radical species in A. aestivalis. With an RP value of 0, Test Formula 12-1 had no UV-inducible free radical potential, whereas 12-2 had a high potential, with RP values of 45.3% in the UVB/A range and 21.9% under pure UVA irradiation. In parallel, the low free radical potential of Test Formula 12-1 did not elicit A. aestivalis
November 2018
Skin reaction score
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