Transepidermal water loss after photodynamic therapy, UVB radiation and topical corticosteroid is independent of inflammation.

Background/purpose: Photodynamic therapy (PDT) and ultraviolet radiation cause an inflammatory reaction of the skin. This may lead to disruption of the skin barrier function. We examined the acute effect of PDT and short-wave ultraviolet radiation (UVB) on the barrier function of the epidermis. Furthermore, we explored the effect on the skin barrier of topical corticosteroid previous to UVB exposure.

Methods: Eight patients with acne vulgaris of the face were treated with PDT two times, and eight patients were left untreated. The transepidermal water loss (TEWL) was measured before treatment and at three control visits after PDT over 12 weeks. Twenty healthy volunteers were irradiated with UVB in two areas on the back. One area was treated with topical high-potency corticosteroid before irradiation. TEWL was measured before, 15 min and 24 h after UVB exposure.

Results: TEWL did not differ significantly between the various visits in each acne group and no significant difference in the TEWL between PDT-treated patients and the control group was found at any visit (P>0.05). TEWL was not significantly altered 15 min and 24 h after a single exposure to UVB and no positive relationship was found between UV-induced erythema and change in TEWL (P>0.05). Application of topical corticosteroid before UVB did not affect the skin barrier function significantly (P>0.05).

Conclusion: Neither PDT nor a single exposure to UVB damaged the permeability barrier function of the skin and no effect on the TEWL was found when topical corticosteroid was applied previous to UVB irradiation.