Burning or vaporizing the cannabis and inhaling the smoke into the lungs is the fastest route to the blood stream. Conventional wisdom is that holding in the smoke increases the effects felt. Recent research shows the opposite; it causes more harm to the lungs without increasing the amount of THC absorbed. Studies done in Australia indicate that 95% of the THC in cannabis is absorbed in the first few seconds of inhaling. Holding in the smoke longer just allows more tar and other noxious chemicals to be absorbed. Take small, shallow puffs rather than deep inhalations. Irritation of the throat and lungs is one of the most obvious adverse effects to the marijuana smoker as is the inevitable cough upon inhaling. The cough is the body's reaction to the irritation of the numerous constituents of the smoke. Prolonged and repeated exposure to these irritants can lower resistance to, and aggravate infections from viruses, bacteria, or fungi. The lesser coughing, the safer the smoke. The fewer puffs the better; the more potent the cannabis used is the fewer puffs required. For these reasons, it is preferable to use only the more potent flower tops, or high grade hash for smoking use.
Despite the obvious dangers of inhaling hot smoke, there is evidence that in some cases (ie. Asthma) smoking could be a beneficial medical use of cannabis. Another advantage of smoking is that it allows the user to control their dosage better as the effects are almost immediate, unlike when eating, or using THC in pill or spray form. In general however, smoking is not the best way to take cannabis, especially for pain, being a less efficient use of the herb than eating. However, many medical users find they appreciate the immediate and pleasurable effects of smoking cannabis and the harm of smoking can be reduced in various ways. One alternative to inhaling smoke is to release the THC through Vaporization; inhaling vapor rather than smoke, see vaporization.