How long is your body polluted with nicotine after you have quit smoking? The short answer is: not that long. The long answer is considerably more complicated. Nicotine is processed by a chemical in the liver called cytochrome P450. It does its job quickly, but how quickly is a matter of how much you smoked and how long you have been smoking. A typical dose of nicotine lasts only a few hours in the body, typically less than 24. Your body is largely free of nicotine within 48 hours of quitting smoking. However, that's not quite the whole story.
Nicotine has a number of longer-lasting physiological effects that cause nicotine withdrawal and prevent nicotine's effects from going away. First, menthol cigarettes inhibit your body's ability to filter out nicotine, meaning that nicotine can remain up to 72 hours in the body after the final menthol cigarette. Nicotine is also a vasoconstrictor, which can result in elevated blood pressure. While the tightened blood vessels last for only about 20 minutes after absorption of nicotine, circulation doesn't return to full capacity for about two weeks after quitting.
One of the biggest reasons that nicotine remains in the body much longer than 72 hours after quitting is that people often need nicotine to quit. Patches and gum both depend upon nicotine to cut down cravings. Simultaneously a stimulant and a relaxant, continued doses of nicotine can force people through periods of heightened, almost manic, need and periods of depression.