Final answer:
The immunoglobulin that binds to mast cells and releases histamine in an allergic reaction is IgE (Immunoglobulin E).
Step-by-step explanation:
The immunoglobulin that would bind to mast cells and release histamine in an allergic reaction is IgE (Immunoglobulin E).
When a person is exposed to an allergen for the first time, their immune system produces IgE antibodies in response. These IgE antibodies bind to mast cells.
On a second exposure to the same allergen, the allergen binds to the IgE antibodies on the mast cells, causing the mast cells to release histamine and other chemical mediators, which elicit an allergic reaction.