Desensitization means to make someone less sensitive through repeated exposure. Desensitization is an important survival mechanism, if you take a job as a roofer, then it is to your advantage to become less frightened by heights over time. Same thing with a doctor, a doctor who can’t stand gore or body parts won’t be that effective, but through repeated exposure, medical students become less and less bothered by cadavers. Doctors working in extreme circumstances, with few tools, have to become inured to the suffering around them due to the lack of pain-killers, to remain effective doctors.
According to The Free Dictionary:
1. To render insensitive or less sensitive.
2. Immunology To make (an individual) nonreactive or insensitive to an antigen.
3. To make emotionally insensitive or unresponsive, as by long exposure or repeated shocks: “This movie in effect may resensitize people who thought they were desensitized to violence” (Steven Spielberg).
4. To make (a photographic film or substance) less sensitive to light.
Examples would be:
When you confront your cadaver during the first week of school, you will begin to learn emotional aloofness. Prospective doctors become desensitized to death’s symbols -bones, blood, corpses, and stench- symbols that disturb most people. Some students become desensitized earlier during premed courses that required them to dissect or even kill living things. In any event, this phase of medical school can still be disturbing. A psychiatrist who interviewed students found that many of them had nightmares about their anatomy experiences.
No matter how great the initial shock, however, it apparently wears off for most students. Before long you become so desensitized that you can eat lunch around the corpse.
Surviving Medical School by Robert H. Coombs (page 137-138)
Deliberate desensitization for the treatment of phobias
Repeated exposure to the feared object or situation desensitizes the patient to the point where they lose their phobia (or it is greatly reduced).
In psychology, desensitization (also called inurement) 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.
And now the repeated exposure is also being done virtually:
Virtual Reality & Cockroaches
Over-exposure to video pornography can also desensitization the viewer to point where the viewer loses sexual responsiveness.