A photo-therapeutic, electrodeless lamp comprises a closed-loop envelope containing an arc generating and sustaining medium. A phosphor coating on the interior of the envelope generates visible radiation in response to excitation from 254 nm radiation. The visible radiation has an energy output in the region of 500-800 nm of ≧12,000 μW/cm2.A reflector formed on a portion of the envelope leaves a window for the emission of the visible radiation and concentrates the power requirements. Means are formed with the lamp for supplying RF excitation to generate the 254 nm radiation. The lamp has an effective area that allows easy operator manipulation and good patient access.