Non-invasive diagnostic evaluation of phototherapeutic effects of red light phototherapy of acne vulgaris

Background: During the past few years, various phototherapeutic protocols with full‐spectrum visible light or selected wavebands have been investigated in the treatment of acne vulgaris with variable results. Methods: Fifteen women suffering from moderate acne vulgaris of the face were exposed to 20 J/cm² of broad‐band red (λ: 600–750 nm) light twice weekly for 4 weeks. In addition, with the aim to improve the present knowledge of the mechanisms of action of phototherapy, we measured skin sebum, pH, hydration and trans‐epidermal water loss (TEWL). Lesions of the trunk were not irradiated and served as controls. Results: A significant improvement of acne lesions and a significant decrease of skin sebum excretion and TEWL of the face were registered at the end of the therapy and at the 3‐month follow‐up visit. The results could be related to a reduced follicular colonization of Propionibacterium acnes, in that it was lethally damaged by photoactivated endogenous porphyrins. Conclusion: The present findings seem to indicate that red light phototherapy may represent an effective, well‐tolerated, safe, simple and inexpensive treatment option for moderate acne vulgaris.