SummaryBackground Frequent bathing leads to a skin barrier damage with various changes in physiological skin parameters. Conversely, ultraviolet (UV) irradiation may improve the impaired skin barrier by reducing inflammatory reactions.
Objectives The aim of this study was to investigate the changes of physiological skin parameters during a therapy with 8-methoxypsoralen (8-MOP) bathing and subsequent UVA irradiation.
Methods Thirty patients with a skin disease without barrier disruption were treated with daily bathing in a 8-MOP solution (0·0005%) and subsequent UVA irradiation. Multiple physiological skin parameters (transepidermal water loss, skin blood flow, skin colour, sebum content, skin hydration) were measured repeatedly on clinically non-affected skin on the back, forearm and forehead. In addition, patch testing with sodium lauryl sulphate (SLS) (0·5%) was performed on the forearm and on the back.
Results We found a moderate but significant disturbance of skin barrier and hydration on the forearm and the back (bathing + irradiation) after increasing dosages of therapy. In addition, SLS testing leads to stronger reactions.
Conclusions We conclude that on clinically healthy skin the impairment of skin barrier by frequent bathing cannot be completely compensated by subsequent UVA irradiation. When conducting a treatment with 8-MOP bathing and UVA irradiation a concomitant therapy supporting the recovery of skin barrier, e.g. with moisturizer, should be performed.