Evaluation of modifications of the traditional patch test in assessing the chemical irritation potential of feminine hygiene products

Background/aims: The first main objective of the work presented in this paper was to investigate ways of optimizing the current arm patch test protocol by (1) increasing the sensitivity of the test in order to evaluate more effectively the products that are inherently non‐irritating, and/or (2) reducing the costs of these types of studies by shortening the protocol. The second main objective was to use the results of these studies and the results of the parallel studies conducted using the behind‐the‐knee method to better understand the contribution of mechanical irritation to the skin effects produced by these types of products. In addition, we were interested in continuing the evaluation of sensory effects and their relationship to objective measures of irritation. Methods: Test materials were prepared from three, currently marketed feminine protection pads. Wet and dry samples were applied to the upper arm using the standard 24‐h patch test. Applications were repeated daily for 4 consecutive days. The test sites were scored for irritation prior to the first patch application, and 30–60 min after removal of each patch. Some test sites were treated by tape stripping the skin prior to the initial patch application. In addition, in one experiment, panelists were asked to keep a daily diary describing any sensory skin effects they noticed at each test site. Results: All protocol variations ([intact skin/dry samples], [compromised skin/dry samples], [intact skin/wet samples], and [compromised skin/wet samples]) gave similar results for the products tested. When compared to the behind‐the‐knee test method, the standard upper arm patch test gave consistently lower levels of irritation when the test sites were scored shortly after patch removal, even though the sample application was longer (24 vs. 6 h) in the standard patch test. The higher level of irritation in the behind‐the‐knee method was likely due to mechanical irritation. The sensory skin effects did not appear to be related to a particular test product or a particular protocol variation. However, the mean irritation scores at those sites where a sensory effect was reported were higher than the mean irritation scores at those sites were no sensory effects were reported. Conclusions:• All four protocol variations of the standard upper arm patch test can be used to assess the inherent chemical irritant properties of feminine protection products. • For these products, which are inherently non‐irritating, tape stripping and/or applying wet samples does not increase the sensitivity of the patch test method. • Differences in irritation potential were apparent after one to three 24‐h applications. Therefore, the standard patch test protocol can be shortened to three applications without compromising our ability to detect differences in the chemical irritation produced by the test materials. • The patch test can be used to evaluate effectively the inherent chemical irritation potential of these types of products. However, this method is not suitable for testing the mechanical irritation due to friction that occurs during product use. • There is no relationship between specific test conditions, i.e., compromised skin and/or testing wet samples and reports of perceived sensory reactions. • However, there seems to be a clear relationship between sensory reactions and objective irritation scores.