Yes - in two ways 1) it works systemically as advertised 2) I sleep for days so I don't notice the discomfort. So that's usually out of the question.
I actually got along well in Colorado when the natives were suffering. I rarely had any issues while growing up in the South. There must be a habituation component in the opposite direction, i.e. the more you are exposed over time, the more likely you are to develop a reaction.