In medicine, desensitization is a method to reduce or eliminate an organism's negative reaction to a substance or stimulus.
This is a macroscopic, organism-level effect and differs from the second meaning of desensitization, which refers to a biochemical effect where individual receptors become less responsive after repeated application of an agonist.
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.
A temporary desensitization method involves the administration of small doses of an allergen to produce an IgE-mediated response in a setting where an individual can be treated in the event of anaphylaxis; this approach, through uncharacterized mechanisms, eventually overrides the hypersensitive IgE response.
[1] Desensitization approaches for food allergies are generally at the research stage.