As an Asthma sufferer this is not news to me. Air 'Fresheners', Diesels and generally poor air quality all impact my breathing. The list of triggers is a long one so I've cut it short, but reserve special mention for the scent ironically named 'Poison' which for some reason really makes my Asthma react badly. Thankfully it seems to have gone from the shelves in recent times!
I also avoid big cities especially in the summer time, both days each year.