What is the characteristic of an IgE mediated reaction?

An IgE mediated reaction is characterized by a rapid onset, generally occurring within minutes to two hours after exposure to an allergen. This type of immune response involves the activation of IgE antibodies, which bind to allergens and trigger the release of mediators such as histamine from mast cells and basophils. The quick response is typically associated with allergic reactions like anaphylaxis, asthma, or an allergic rhinitis, where symptoms can manifest almost immediately.

The timing is critical in distinguishing IgE mediated reactions from other types of allergic responses. For instance, other types of hypersensitivity reactions, such as those that are mediated by T cells (Type IV hypersensitivity), have delayed onset and may occur after two hours to several days. Thus, the immediate nature of IgE involvement is a defining characteristic that supports the correct choice. This rapid response can lead to symptoms such as hives, swelling, difficulty breathing, or gastrointestinal distress, rather than chronic symptoms or localized effects only on skin health.