Desensitization is a method to reduce or stop a reaction to something. For example, if a person with diabetes has a bad allergic reaction to taking a full dose of beef insulin, the doctor gives the person a very small amount of the insulin at first. Over a period of time, larger doses are given until the person is taking the full dose. This is one way to help the body get used to the full dose and to avoid having the allergic reaction to beef origin insulin. 2) In pharmacology, it is the loss of responsiveness to the continuing or increasing dose of a drug. Also termed tachyphylaxis, down-regulation, fade or tolerance. See also tolerance in physiology or tachyphylaxis.