Desensitization is a method to reduce or eliminate an organism's negative reaction to a substance or stimulus.

In medicine

For example, if a person with diabetes mellitus 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.

In pharmacology, desensitization is the loss of responsiveness to the continuing or increasing dose of a drug. Also termed tachyphylaxis, down-regulation, fade or drug tolerance. See also physiological tolerance.

In psychology

In psychology, desensitization (or graduated exposure therapy ) is a process for mitigating the harmful effects of phobias or other disorders. It also occurs when an emotional response is repeatedly evoked in situations in which the action tendency that is associated with the emotion proves irrelevant or unnecessary. Agoraphobics, who fear open spaces and social gatherings outside their own home, may be gradually led to increase their interaction with the outside world by putting them in situations that are uncomfortable but not panic-provoking for them. Mastering their anxiety in very small doses can allow them to take greater steps to self-reliance. Desensitization can be an alternative or a supplement to anxiety-reducing medication.

In animals

Animals can also be desensitized to their rational or irrational fears. A race horse who fears the starting gate can be desensitized to the fearful elements (the creak of the gate, the starting bell, the enclosed space) one at a time, in small doses or at a distance.