Final answer:
In allergic rhinitis, the Type 1 hypersensitivity reaction is mediated by the immunoglobulin IgE. IgE antibodies cause mast cells to degranulate, releasing histamines and causing allergy symptoms.
Step-by-step explanation:
The immunoglobulin that mediates the type 1 hypersensitivity reaction involved in allergic rhinitis is IgE. Type I hypersensitivity reactions, such as those seen in allergic rhinitis, involve IgE antibodies against soluble antigens, leading to mast cell degranulation. Upon initial exposure to an allergen, IgE synthesis occurs. When exposed again to the same allergen, the IgE on the surface of mast cells binds the antigen and stimulates the cells to release histamines and other substances that cause the symptoms of allergy, like sneezing and itchy, watery eyes.
Type II hypersensitivity reactions are mediated by IgG and IgM antibodies directed against cellular antigens, causing cell damage with the assistance of other elements of the immune system. These reactions differ from Type I as they do not involve IgE or mast cell degranulation.