Daylight PDT vs Red Light Therapy in Acne Treatment

person reaching towards sun
person reaching towards sun
The efficacy and tolerability of DL-PDT and C-PDT for acne treatment was compared.

Daylight (DL) photodynamic therapy (PDT) and conventional PDT (C-PDT) with red light led to similar and significant reductions in inflammatory and noninflammatory lesions in patients with facial acne, according to findings from a split-face trial published in the Journal of Cosmetic Dermatology.

Studies have indicated DL-PDT may be associated with less pain than C-PDT with red light. In a study of 15 patients with acne vulgaris, a small team of researchers from Israel compared the efficacy and tolerability of the 2 PDT strategies using a split-face approach.

Patients in the study underwent 4 treatment sessions every 3 weeks. Before each session, the facial skin was degreased with a 70% alcohol solution, and a chemical sunscreen was applied to the right side of the face. A 5-aminolevulinic acid gel at 20% concentration was then applied to the entire face. Participants were asked to spend 30 minutes indoors with an occlusive dressing consisting of plastic film on their face.

Researchers covered the left side of participants’ faces with a light-impermeable aluminum foil dressing and asked the participants to spend 2 hours outdoors in the hospital garden. This exposed the right side of the face to natural sunlight.

Participants then had their left side of their faces exposed to red light at 630 nm (total light dose, 75 j/cm2), while the right side of the face was occluded with the aluminum foil dressing. All patients were asked to avoid sun exposure for 48 hours after PDT and were instructed to apply a mineral-based sunblock with a sun protection factor of 50 or higher throughout the study period.

Every patient in the study was White, and the cohort had a Fitzpatrick phototype range of 2 to 3. The mean age of the population was 23.3±6 years (range, 15-34 years), and the majority of patients were women (60%). Approximately 40% of participants previously received treatment with isotretinoin.

The side of the face exposed to C-PDT demonstrated significant changes in the numbers of comedones (P =.017), papules (P =.004), and pustules (P =.001), as well as a significant improvement in the global evaluation acne (GEA) score (P =.005).

The side of the face exposed to DL-PDT also showed significant changes in the numbers of comedones (P =.002), papules (P =.001), and pustules (P =.002), as well as a significant improvement in the global evaluation acne (GEA) score (P =.005).

Treatment with DL-PDT demonstrated a significantly greater reduction in the number of pustules from baseline to end of treatment compared with C-PDT (P =.023). The researchers also reported a significant correlation in the change in GEA score on both the right and left sides from baseline until follow-up (P =.008).

The most frequent adverse reaction was mild erythema, which was deemed more intense for the C-PDT side. Erosions and erythema were also more severe on the side exposed to C-PDT. Patients reported less pain on the side of the face exposed to DL-PDT. In addition, there was significantly less downtime associated with DL-PDT (1.4 vs 4.1 days; P =.001).

Limitations of this study included the small number of patients, the large variability in terms of acne characteristics and severity, and the lack of a non-PDT control arm.

Despite these limitations, the researchers noted that the DL-PDT regimen may be more accessible for patients and clinicians, as patients do not have to return to the clinic as frequently and providers do not need to purchase a light source for the therapy.

The researchers added that clinical “guidelines and protocols should be established for this treatment option for acne vulgaris.”


Slutsky-Bank E, Artzi O, Sprecher E, Koren A. A split-face clinical trial of conventional red-light photodynamic therapy versus daylight photodynamic therapy for acne vulgaris. J Cosmet Dermatol. Published online August 1, 2021. doi:10.1111/jocd.14359