Hmmm... Speaking as someone with a keener sense of smell than most non-smokers even when I smoked 2 pks a day, I'd say it's possible the person is one like me, "super-taster" or "super-smeller" who perhaps also suffers from both allergy, and hypochondria -- having this extreme reaction to smell, and having allergies, tends to lead one to varying levels of hypochondria about strong odors and allergens. So it probably is some of both: outrageously keen sense of smell, and somewhat psychosomatic. And no, nothing much can be done about people like that, except avoid them, or if one of them oneself, become a virtual hermit.
Andria