Skin physiology during daylight photodynamic therapy with additional fractional laser therapy

Daylight photodynamic therapy is currently the preferred treatment for actinic keratosis due to its greater effectiveness and a lower level of pain compared to conventional photodynamic therapy. To enhance the effectiveness of the therapy, especially for hyperkeratotic forms, various pre-treatments are currently available, primarily fractional laser therapy. Until now, there have been few studies investigating skin physiology after photodynamic therapy and fractional laser treatment. The aim of the study was to investigate the skin physiological changes in daylight photodynamic therapy with and without fractional laser pre-treatment. Thirty patients with actinic keratoses were recruited at the Clinic for Dermatology, SLK Clinics Heilbronn, Germany. On the ventral right or left forearm of the patients, four fields of 3 x 3 cm each were randomly assigned to: daylight, fractional laser with daylight, daylight photodynamic therapy with 10% 5-aminolevulinic acid hydrochloride gel, and daylight photodynamic therapy with fractional laser with 10% 5-aminolevulinic acid hydrochloride gel. Redness, corneometry, and transepidermal water loss were measured before treatment, 30 minutes, 24 hours, seven days and 14 days after treatment. Compared to the effects of daylight photodynamic therapy alone, daylight photodynamic therapy with fractional laser caused more pronounced skin changes, with the increase persisting for up to 24 hours for transepidermal water loss values and up to 14 days for skin redness and dryness. Additional fractional laser was shown to intensify inflammatory processes and damage the skin barrier. This enhanced biological effect could also lead to an increased clinical effect on actinic keratoses.