Tobacco contains the drug nicotine, which is a central nervous system stimulant.
Many of the physical symptoms that tobacco users experience when they reduce or quit are the result of the nervous system returning to normal after the effects of using tobacco, nicotine and smoke. These symptoms can start within 20 minutes after you last used tobacco, and usually peak by the second or third day. Nicotine is a water soluble drug, and generally leaves the body within three to five days. However, the trauma from the effects of the withdrawal, the continuing process of the body cleaning itself out from years of tobacco use, and the possible contaminates still left in the tar residue in the lungs, can cause health effects for days or weeks longer. Usually the tobacco user starts to feel welcomed relief within the first two weeks.