How can a doctor tell if you smoke by looking at your nails (not fingers)$?

Your nails turn yellowHow can a doctor tell if you smoke by looking at your nails (not fingers)$?
some have yellow from smoke stain,some finger are turned from holding them and some have bluish color under the nails


depends on ageHow can a doctor tell if you smoke by looking at your nails (not fingers)$?
when you smoke your nails start turning yellow i know this cause in my house theres 4 of us and everyone smokes but me i can tell the difference between nails
if you are not getting an adequate oxygen supply your nails will become odd shaped and the nail beds will be blue tinged
I can tell a smoker without looking at their nails or fingers. Their skin looks gastly.