TABLE 3.

Included studies demonstrating the irritation effects of n‐propanol and isopropanol on components of the stratum corneum

					Conclusion
Intervention	Substance	Population, sex	Measurement	Author/year/location	Clinical outcome	Skin physiological measurements
NMF analysis	60% aq. n‐propanol 0,5% aq. SLS	25 (16F, 9M) healthy	D Squame	Angelova‐Fischer et al/ 2016/Netherlands 31	Reduction of NMF levels −55.4% with n‐propanol and −79.2% Pretreatment with occlusion −60.8% and −87.4%, respectively
Patch test	0,5% SLS 0,15% sodium hydroxide 60% n‐propanol 2,0% acetic acid	8 (5F, 3M) healthy	Tewameter Chromameter Corneometer D Squame AFM (atomic force microscopy) DTI (dermal texture index)	Soltanipoor et al/ 2017/Netherlands, Germany, Denmark 45	55% reduction of NMF levels with n‐propanol, but as high as 75% with repeated exposure of SLS Changes in corneocyte topography with n‐propanol, SLS and NaOH after 96 hours with increase in DTI and circular nano objects	n‐propanol caused only slight changes in TEWL and erythema, but a significant decrease in skin capacitance after 96 hours
Keratinocyte culture	0%, 0,1%, 0,5%, 1%, 2% – 10% increments of 70% w/w alcohol (ethanol, n‐propanol, isopropanol) IL‐1a DuoSet ELISA development kit and TNF‐a DuoSet development kit		MTT assay	Cartner et al/2016/USA,UK 26	Marked cellular toxicity and significant TNF‐α and IL‐ 1α release by the skin residential cell with n‐propanol, followed by isopropanol and ethanol
Occlusion‐modified tandem repeated irritation test	n‐propanol (30%, 45%, 60%, 75% aq.)	20 (16F, 4M) healthy 20 (17F, 3M) atopic dermatitis	D‐SQUAME (NMF analysis)	Angelova‐Fischer et al/ 2019/Germany, Austria, Netherland, Croatia 44	Cumulative exposure to n‐propanol reduced significantly the NMF levels in healthy and atopic skin equally

Note: ELISA, enzyme‐linked immunosorbent assay; F, female; M, male; MTT assay, cell viability assay; NMF, natural moisturizing factor; SLS, sodium lauryl sulfate.