Regional Differences of Cutaneous Irritation and Its Effect on Skin Barrier Recovery

Plain-language summary

Irritant contact dermatitis induced by sodium lauryl sulphate (SLS) is often used as a model for testing efficacy of various topical preparations. Aforementioned model is standardized and described in guidelines, but it is not explicitly stated where the irritation should be induced. Published clinical trials usually irritate volar aspect of forearms or upper back. Also, lower back and dorsal aspect of forearm are sometimes used. Skin parameters vary depending on anatomic location of measured skin. There is a difference in stratum corneum thickness, hydration and transepidermal water loss across different locations, including between volar forearm and upper back. Furthermore, regional difference in skin response to irritation by tape stripping and benzalkonium chloride were observed. Such differences are also possible in SLS irritation model. One study has shown higher, but not statistically significant, response of back in comparison to forearms, but it had a very small sample size (n=9). Moreover, there are regional variations of topical preparations absorption. Hydrocortisone had 1,7 times higher absorption when applied to upper back in comparison to forearms. Those variations could be explained by different corneocyte size and number of their layers between back and hands. Skin baseline properties and response to irritation seem to be dependent on anatomic position. Those differences could mean different response to treatment. Since published trials only tested efficacy of various preparations on one anatomic location, it is possible their results would be different if tested on other body parts. It could limit validity and usefulness of conducted trials. The aim of this study is to determine if there are regional differences of skin response to irritation and emollient cream treatment in irritant contact dermatitis model.

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