Overtime individuals develop a toleranceThe reaction of the body to an increased amount of a controlled substance. When an ever-greater quantity of the substance is necessary to obtain a high, the body has developed a greater tolerance. More to substances used regularly. In some cases, this can contribute to tolerance to other substances with similar functions or effects as well. Due to cross-tolerance one may have a tolerance to a drugA name for a wide variety of chemical substances capable of altering the function of your mind and body in significant ways. These can include over the counter prescriptions, alcohol, and controlled substances. Most drugs are either physically and/or psychologically habit-forming. More they have never taken.