Within 12 hours, the level of poisonous carbon monoxide in your body from cigarettes has returned to normal.
Over the next few months, your lungs will regain their ability to remove pollutants efficiently, thereby reducing your risk of infection. Your ability to taste and smell will improve, and that chronic sinus congestion should disappear.
By the first anniversary of your last cigarette, your risk of heart disease should be about half of a smoker's. (By your 15th anniversary, it should be about the same as the risk for someone who never smoked.)
And within a decade, your risk of dying from lung cancer will have dropped by half. It will never drop as low as the risk faced by those who have never smoked, but it will come pretty close.
Another benefit of quitting also begins immediately, says Norman Edelman, MD, chief medical officer of the American Lung Association. "As soon as you take a shower and change your clothes, you stop smelling," he tells WebMD.
"You may cough more, but that shouldn't be a concern because it means you're clearing the gunk out of your lungs and opening your airways," says Edelman. "In a few weeks you should begin to notice an increase in your exercise tolerance."