I am on this page because I work for a paramilitary organization that is very much into SERE training (learning to resist interrogation/torture at all costs). We are testing some cutting-edge methods but we can't change the fact that everyone has a breaking point. Unless...something can permanently reduce the human pain threshold, creating super soldiers! Capsaicin has almost no side effects and seems to be able to do this to the nerves it encounters, without making them completely numb. Meaning, just because you eat hot peppers doesn't mean you can't feel it when you're getting your teeth pulled. It's a long term, gradual solution.
I take oral cayenne pills 3-6 times a day as a naturopathic treatment for a bleeding problem. It works AMAZINGLY and does what my prescription cannot, with no noticeable side effects. I'm about to scrap the prescription altogether and just use Capsaicin.
I think people should stop being dogmatic about medicine and conduct their own experiments sometimes. Do whatever works, especially if the substance in question has been proven harmless through human use over centuries. There may be some unforeseen effects, but if entire cultures and societies thrive despite them, it's not a big deal.
Recently, in a SERE training simulation, concentrated capsaicin cream was used to make me think I was on fire. The interrogator had cut off my hair and was burning it while I was blindfolded to reproduce the smell of burning flesh. Creative psychological technique. It hurt so much that I was convinced! But later on in the simulation, injury to the Capsaicin-affected areas hurt less. The interrogator assumed they would hurt more because they had been irritated. His pharmacological miscalculation was helpful to me but I was thinking, "OMG, he must have burned me so bad that the nerves don't work! He's not supposed to do that in a simulation!!!"
That got me thinking about the military application. It could be applied daily all over the body with a few exceptions, such as eyes and orifices, however subdermal Substance P would still be there, and the problem is, the enemy would find out about our methods and know where to inflict pain that we would not be immune to.
What we really want is a way to dilute Substance P in the brain itself, so that the pain threshold of the entire nervous system is evenly increased. I have talked to a few medical professionals and they imply that Capsaicin does not do this, however they don't seem to know quite what they're talking about. I think I will run some experiments. Give some subjects capsaicin pills and some placebo and test the response to pain, first while the Capsaicin is active in their bodies, and second after 30 days of taking it and 10 days without. Or something like that.
Being completely impervious to pain is dangerous, but Capsaicin is not going to do that to you. If you increase your pain threshold with a substance, you would know to respond to small amounts of pain for your own safety. There will still be an indicator that is greater or lesser compared to the stimuli, it will just be more subtle, and you would have to learn your body's new language and adjust your response.