Could it be something of a misnomer? The fumes from expended nitro compounds can cause vicious headaches...in extreme cases, a debilitating headache similar to migraine. High percentage dynamite is brutal in underground mining and tunneling. Not everyone suffers from it, and eventually the new miner builds a resistance to it. I worked for an underground mining outfit in Idaho briefly, the miners would shoot their shot just at quitting time, let the face ventilate overnight before going back the next day to muck out. New miners were advised to smear a little dynamite on their hardhat headband to get over 'powder headache'. I think it was nothing more than a cruel joke.
