It can be safe; if you're in good oral health and follow the instructions on the package– BUT you definitely need to consider a few things. First of all, since the "light" from the tanning bed has almost nothing to do with the results you'll achieve (see our article on whitening lights) there's no reason, other than convenience, to tan while IN the bed. Next, your teeth whitening results are provided by a high strength teeth whitening gel - of up to 44% Carbamide Peroxide - that you're using without the supervision of a dental professional and that can cause sensitivity and or true discomfort if you're not in good oral health. And finally, tanning beds themselves raise your risk of skin cancer, so if melanoma runs in your family or you use tanning beds multiple times per month, you need to be careful anyway. So, if you're asking if teeth whitening in a tanning bed is safe - technically it is. But if you're asking if it's a good idea? Probably not.