Phototherapy with blue (415 nm) and red (660 nm) light in the treatment of acne vulgaris. Papageorgiou P, Katsambas A, Chu A. British Journal of Dermatology, 2000; 142(5): 973–978.
Why this study is foundational
Published a quarter-century ago from Hammersmith Hospital in London, this is the trial that established combined blue-and-red phototherapy as a subject worth studying, and nearly every combined-mode device since traces its rationale here. It is also an early example of comparing light not just to nothing, but to an established topical treatment.
Design
- Participants: 107 people with mild to moderate acne vulgaris.
- Arms: four, blue light alone (415nm), mixed blue and red light (415nm + 660nm), cool white light, and 5% benzoyl peroxide cream.
- Protocol: 15 minutes of daily exposure from portable home light units, for 12 weeks.
- Endpoint: change in counted inflammatory lesions.
Findings
After 12 weeks, the blue-plus-red group showed a 76% mean reduction in inflammatory lesions, outperforming blue light alone (about 58%), white light (about 25%), and the benzoyl peroxide arm. The proposed logic of the pairing: blue light acts on porphyrins produced by Cutibacterium acnes at the surface, while red light contributes at greater depth.
Limits worth stating
- A single trial from 2000, with modest arm sizes once 107 participants split four ways; later reviews report supportive but similarly modest-scale evidence.
- White light served as the closest thing to a placebo arm, not a true sham.
- The study describes a clinical phototherapy protocol on a diagnosed condition; it is summarized here as research history, not as a description of what any cosmetic device does.
Source: British Journal of Dermatology, 2000; 142(5): 973–978. PMID: 10809858