A reader asks:

I take a low dose birth control pill and have been advised to stay out of the sun to avoid brown marks (“mask of pregnancy”) on my face. Will a light box cause the same marks?


The vast majority of drug-light interactions in the skin are triggered by ultraviolet (UV) radiation. An acceptable light box assiduously filters out such energy, thereby eliminating or greatly reducing the risk of photosensitization. Any plastic screen on a light box will filter out some UV, but how much is a question that requires spectroradiometry. Spectroradiometry is a specialized laboratory technique that measures energy transmission throughout the UV and visible range of light wavelengths.

Beware UV-free Claims

Unfortunately, many manufacturers claim their systems are “UV-free” without providing supporting data. We know of only two light box filters that have been demonstrated to do the job adequately (OP-3 and polycarbonate based). The cautious consumer will look for those specifications or demand to see a printout of a spectrogram that shows near-zero transmission of wavelengths below 400 nanometers. All that said, there are some medications that photosensitize in the short-wavelength “far blue” visible range between 400-450 nanometers, so it is important for your doctor to ascertain whether a UV-filtered light box may still pose a risk.