I don't smoke. Never have. Did try it once to see what all the fuss was about and decided it was a disgusting habit and never tried it again.
My parents smoked, though. For the first 21 years of my life, I was sucking back second hand smoke on a daily basis - both my parents were two-pack-a-day smokers. As a result, I developed severe allergies to just about anything I breathed, and ended up having to take allergy shots for a number of years, which have alleviated my reactions somewhat. I should go back for another round, but I can't afford to.
Before and after leaving home, and throughout my 20s and 30s, I suffered from ear infections (a side-effect of second hand smoke) and had one chest infection after another, culminating in a really bad bout of pneumonia. Once I stopped taking antibiotics, however, the frequency and severity of the chest infections diminished. I still get ear infections, but not as often. However, I'm still really susceptible to any respiratory ailment and particularly to the flu, and each round of flu has been worse than the last (the last time being 1998, which lasted for nearly four weeks. I should have been in hospital, but was too sick to get up and call an ambulance!), so now I'm first in line when flu shots become available in the fall.
Smoking is a really filthy habit that affects more people than just smokers. I wish smokers would understand this instead of whining about how hard done-by they are whenever a new anti-smoking by-law comes out restricting the public places in which they are allowed to smoke.