Imagine, for a moment, that you live with a semi-deaf roommate. This roommate really enjoys music, but has a hard time hearing it, so he cranks up the volume to a level that is comfortable and enjoyable for him.
You, as a person who is not hard of hearing, have a much lower threshold for what is comfortable and enjoyable. Roommate is rocking out while you are rolling on the floor, clutching your head in agony. The sensory overload is causing you real pain. When you ask if the roommate can turn it down, he looks at you incredulously. "It's not THAT loud, hell, I can barely hear it!" You try to explain that, because his hearing isn't as acute as yours, your volume tolerances are different. He scoffs at this, telling you that you're making it up, and to stop being such a sensitive goddamn pussy, and to stop trying to control him with your stupid hypochondriac bullshit. He then turns it up even louder, flips you the bird, and subsequently refuses to ever turn the stereo off at all, just to spite you.
That, my friends, is what it is like to have a very sensitive sense of smell in a world where everyone and their dog is slathering on several layers of perfumed products.
Maybe you don't smell it quite as acutely. Maybe you think we're making this up. But when someone is trailing their cologne behind them like Princess Diana's bridal train, for some of us with sharp noses, it's the equivalent of someone screaming in your ear at the top of their lungs. The sensory overload hurts. It gives us headaches, just like the aforementioned roommate's music would give most other people headaches. Just because you aren't able to smell things as well as we do, doesn't mean that we are imagining this.
The overload of our olfactory senses causes a reaction--our sinuses fill, our noses run, our eyes water. This is a neurological reaction that is designed to reduce the waves of sensory input entering our noses. In fact, there is a certain nerve, the trigeminal nerve, that, if aggravated, can actually cause the nostril on the afflicted nerve's side of the face to run, the eye to water, and the sinuses--just on that side--to fill (this can be trigeminal neuralgia, or a cluster headache)--just from a nerve going haywire!
So, yes, when we get too much olfactory input, there is a PHYSICAL reaction, just like when your pupils constrict and your eyes hurt if you are in light that is too bright. If we are in a place that we cannot leave, such as our own homes, or a workplace, we are subject to pain and discomfort that cannot be mitigated. This is why many of us are sensitive to perfumes, and why we ask that others be more subtle with their scents. We're not trying to be mean to you, or to control you, we are trying to save ourselves from terrible headaches. Why is that too much to ask?