Final answer:
Pollen allergy falls under the category of immediate hypersensitivity, which is a type I hypersensitivity reaction. It is characterized by a quick immune response following exposure to an allergen after sensitization. Allergies are not autoimmune reactions, immunodeficiencies, or infectious diseases.
Step-by-step explanation:
Allergy to pollen is considered a hypersensitivity reaction of the immune system, specifically classified as a type I hypersensitivity or immediate hypersensitivity. This occurs when an individual who has been sensitized to an allergen, such as pollen, experiences an immune response almost immediately upon exposure to that allergen. The first exposure to the antigen prompts the production of IgE antibodies, which sensitize mast cells and basophils, leading to a rapid allergic reaction upon subsequent exposures to the allergen.
Hypersensitivity reactions are part of a spectrum of inappropriate immune responses to harmless foreign particles or self-antigens and encompass immediate-type (allergy), delayed-type, and autoimmunity. Allergies are not classified as autoimmune reactions, which involve the immune system mistakenly targeting the body's own tissues, nor are they a form of immunodeficiency, which denotes a failure or insufficiency in the immune response. Furthermore, allergies are not infectious diseases but rather inappropriate immune responses to environmental substances that are typically harmless to most individuals.