Which immunoglobulin is known for its role in allergic reactions?

IgE is the immunoglobulin primarily associated with allergic reactions. It plays a crucial role in the immune system's response to allergens, such as pollen, dust mites, and certain foods. When a person is exposed to an allergen, IgE antibodies bind to it, which triggers the release of histamines and other chemicals from mast cells and basophils. This release is responsible for the symptoms commonly associated with allergies, including itching, swelling, and respiratory issues.

IgA is mainly found in mucosal areas, like the gut and respiratory tract, and protects against infections; IgM is the first antibody produced in response to an infection and is involved in the initial immune response; IgD is less understood but is believed to play a role in the activation and regulation of B cells. Therefore, while all these immunoglobulins have important functions, IgE's specific role in mediating allergic reactions makes it the correct answer.