Topical ALA and Blue Light

Topical ALA and blue light (peak 417 nm) has yielded more modest efficacy in reported studies, likely due to the shallower penetration depth of these shorter wavelengths. In one study, blue light therapy once weekly for 2 weeks resulted in 25% improvement for light alone, and 32% improvement following ALA application prior to illumination [9]. Simi­larly, another study demonstrated a 43% acne clearance rate for blue light when it alone was applied once a week for 4 weeks, as opposed to a 60% response when ALA incubation was added prior to illumination for 30-60 min [11]. In another study of 18 patients, short incubation ALA with activation by blue light or intense pulsed light (IPL) demonstrated greater improvement in the IPL group as compared to blue-light group [20]. Topical ALA for a short 1-hour incubation followed by LP PDL as compared to blue light also demon­strated lower effectiveness in the ALA blue-light group [4]. Recently, the phase IIa FDA trials of topical ALA and blue light also failed to demonstrate higher efficacy in the ALA blue-light group as opposed to blue light alone, except when subgroup analysis was per­formed. The phase IIb trials of topical ALA comparing blue light and LP PDL to controls would be helpful in clarifying these observations.