Sorry but I don't think nobody knows. It depends on so many factors. I can't give any advice, really. Just start slow and watch reactions. What effect do you get when you put the redlight in the mouth?
Its a nice good feeling. Like a weak dose of heroin being injected into an uncomfortable body part. I would think the skin inside the mouth would absorb substances, as well as light, faster and better then the rough thick skin on the outside of the body. Would this feeling be due to a rise of co2 and lowering of cortisol in the blood of the exposed area?