Blue light phototherapy in the treatment of acne

Background: Blue light irradiation is known to be effective against acne. However, the profile of a good candidate is still unclear. Methods: Thirty-one Taiwanese with symmetrical facial acne were irradiated with blue light on one side of the face selected randomly twice weekly for 4 consecutive weeks. The other half of the face was left untreated as control. Parameters, including scar type, pore size, and facial follicular porphyrin fluorescence intensity, were documented. The severity of acne was assessed before the treatment, after two, four, and eight sessions of treatment, and 1 month after the treatment was completed. Results: Compared with the non-irradiation side, eight sessions of blue light irradiation were effective in acne treatment (P<0.001). Gender (P=0.471), scar type (P-values of pitted, atrophic, and hypertrophic type were 0.688, 0.572, and 0.802, respectively), pore size (P=0.755), and pretreatment fluorescence intensity (P=0.656) could not be used as predictive factors of therapeutic effectiveness. Compared with pretreatment, nodulocystic lesions tended to worsen despite treatment. In addition, the therapeutic effectiveness was not related to the fluorescence intensity change (P=0.812). Conclusions: Blue light irradiation is effective in acne treatment. Patients without nodulocystic lesions are better candidates for blue light irradiation.