A smaller percentage of users smoke cigars and pipes, and generally do not inhale, since cigar and pipe tobacco is potent enough for the nicotine in the smoke they produce to be readily absorbed in the mouth. Chewing tobacco is taken in similar fashion. Both products stimulate saliva production, and users must spit frequently to clear the mouth of excess saliva and tobacco which has lost its flavor. Smokeless tobacco is popular among athletes, especially baseball players, who use it to prevent their mouths from becoming dry during games. Since this form of tobacco is associated with cancers of the mouth and neck , many high school and college athletic associations have banned it, and professional leagues are now discouraging its use.
Passive smoking is the process that causes non-smokers to inhale smoke involuntarily.
This smoke has neither passed through a filter nor through the lungs of a smoker and is therefore extremely potent, containing more tar, nicotine, particles, and gases than inhaled smoke. Sidestream smoke can cause respiratory distress and allergic reactions, as well as lung cancer. Smoking or chewing tobacco stimulates the habitual user, creating a pleasurable sensation not unlike a high. The effect is generally described as relaxing, although smoking releases the hormone epinephrine, which may create stress in the user. Nicotine, perhaps the most commonly recognized ingredient of tobacco, is an addictive central nervous system stimulant.