Which of the following terms best describes the abnormal reaction of a body to allergens?

The term that best describes the abnormal reaction of a body to allergens is hypersensitivity. Hypersensitivity refers to an exaggerated immune response to a substance that is typically harmless, such as pollen, certain foods, or insect stings. This abnormal reaction can manifest in various forms, including allergies like hay fever, asthma, or anaphylaxis, where the body's immune system reacts too strongly to an allergen.

Desensitization involves gradually exposing a person to increasing amounts of an allergen with the goal of reducing the sensitivity to that allergen over time. While it aims to address hypersensitivity, it doesn't define the abnormal reaction itself.

Tolerance is the ability of a person's immune system to ignore a particular allergen without triggering a significant reaction. This also contrasts with hypersensitivity, as it indicates a normal immune response to a substance.

Resistance generally refers to the ability to withstand or fight off infections or diseases, rather than an overactive or abnormal reaction to allergens. In the context of allergies, the term does not apply as it doesn't capture the essence of the body's exaggerated response.

Thus, hypersensitivity is the most appropriate term for describing the abnormal reaction of the body to allergens.