Final answer:
Allergies are caused by an overreaction of the immune system to antigens, which are typically harmless substances. The correct answer is A) Allergies, with an allergy to pollen being an example of immediate hypersensitivity. Allergies can cause symptoms ranging from mild to severe, such as sneezing, itchy eyes, and life-threatening anaphylaxis.
Step-by-step explanation:
Allergies are an overreaction to an antigen and can cause anything from sneezing to death. The correct answer to the question is A) Allergies. An allergy is a condition where the immune system responds with an inflammatory reaction to a typically harmless substance in the environment, known as an allergen. Classic examples include pollen, which can cause allergic reactions such as sneezing, a runny nose, and itchy, watery eyes.
An allergy to pollen is classified as immediate hypersensitivity, which is an over-reactive immune response causing symptoms shortly after exposure to the allergen. This contrasts with autoimmune diseases, infections, and cancers, each of which involves different mechanisms of immune system dysfunction or responses to harmful pathogens.
Hypersensitivities, such as those seen in allergies, are misdirected immune responses to harmless foreign particles. These immune responses can result in a variety of symptoms, which can range in severity from mild discomfort to life-threatening reactions like anaphylaxis. Understanding allergies and their triggers is essential in managing them effectively.