Multicentre study for the development of an in vivo model to evaluate the influence of topical formulations on irritation

Abstract

Although skin protective products to prevent irritant skin reactions are in wide use, neither standardized test models to prove differences in efficacy exist, nor has the quality or the reproducibility of results been evaluated in a multicentre approach. This should be mandatory when developing or testing skin care products. Therefore, we have designed a multicentre study in an approach to find a standardized test procedure for the evaluation of skin protective products. In this irritation study, a repeated short-time occlusive irritation test (ROIT) with a standardized protocol has been evaluated in 2 phases (12 days and 5 days protocol) in 4 (n=20) respectively 6 (n=33) skilled centres. The skin reaction was induced by 2 irritants (0.5% aq. SLS and toluene, 2x a day for 30 min). Its modification by 3 different cream bases with different hydrophilicity was analyzed. The irritation was monitored by bioengineering methods (TEWL measurement, colorimetry) and by clinical scoring. The evaluation showed that significant results could already be achieved with the 5-day protocol. Furthermore, in spite of the expected inter-centre variations due to heterogeneity of the individual threshold of irritation, interpretation of clinical score, and inter-instrumental variability, the ranking of the vehicles regarding reduction of the irritant reaction was consistent in all centres.

Tandem Repeated Application of Organic Solvents and Sodium Lauryl Sulphate Enhances Cumulative Skin Irritation

“…In addition, the break-off criteria introduced in the current study may have played a role, since too excessive an irritation was averted by premature termination of irritation. On the other hand, in the previous studies it was also noted that toluene alone, when applied twice daily, did not induce a relevant increase in the TEWL [18,29]. In our current study, we can confirm that organic solvents characteristically do not cause deterioration of the skin barrier function, which is most probably due to the unique effect of these chemicals on the intact stratum corneum, damaging it to a lesser extent [6].…”

Effectiveness of Barrier Creams against Irritant Contact Dermatitis

“…We identified 39 controlled trials (table 1) investigating the effect of BCs against skin irritants in a total of 929 volunteers (172 men, 279 women and 481 unspecified subjects) with healthy skin (n = 28), hand dermatitis (n = 1), skin sensitized to a specific allergen (n = 4) and 1 study on latex glove allergens [6,15,16,17,18,19,20,21,22,23,24,25,26,27,28,29,30,31,32,33,34,35,36,37,38,39,40,41,42,43,44,45,46,47,48,49,50,51,52]. From these 39 papers, studies on excised skin [18,24,40,41,43,46] have been discarded, and only trials on subjects with healthy and non-sensitized skin were retained, reducing the list to 27 papers detailed in table 1.…”

“…The contact time of irritants ranges from 5 s to 24 h but the most frequent contact time is 30 min (n = 11) and 24 h (n = 4). Repetitive irritation tests, including repetitive occlusive irritation tests and tandem repetitive irritation tests, were performed in 11 studies [22,23,26,30,31,32,36,38,42,44,50]. The assessment methods often consist of clinical scoring of irritation after cutaneous patch tests (n = 17) and bioengineering methods which are habitually evaporimetry (n = 17), colorimetry (n = 12), corneometry (n = 7), flow velocimetry by Doppler laser (n = 6), spectrometry (n = 3) or other more infrequently used methods.…”

“…We must note that Kütting et al assessed their subjects only by clinical scoring while, according to the recent paper of Sadhra et al [52], it seems that clinical assessment is not sufficient without bioengineering. For the latter, it is also suggested that biophysical studies may provide information on changes in the skin condition before any visible dermatological changes occur [52] while other authors believe that clinical scoring is more appropriate at work [36,60]. According to several authors, the measure of transepidermal water loss is the best parameter of the barrier's alteration, even if some substances alter this parameter only slightly [22,35,36,61,62].…”

Impact of wet work on epidermal barrier (TEWL and stratum corneum hydration) and skin viscoelasticity in nurses

“…Uważa się, że parametr TEWL jest wiarygodnym i czułym wskaźnikiem naruszenia integralności bariery naskórkowej (14). Również pomiar pojemności elektrycznej skóry jako parametru odzwierciedlającego naskórkową zawartość wody wskazywany jest jako ważne narzędzie obserwacji wczesnych zmian u pracowników narażonych na czynniki drażniące (12).…”