What term describes an extreme sensitivity reaction to normally harmless substances?

The term that describes an extreme sensitivity reaction to normally harmless substances is "allergy." Allergies occur when the immune system mistakenly identifies a benign substance, such as pollen, dust mites, certain foods, or pet dander, as a threat. In response, the body produces a range of symptoms that can vary in severity, including sneezing, itching, hives, or even anaphylaxis in severe cases. This abnormal response indicates that the immune system is overreacting to substances that should typically be harmless, leading to the categorization of this reaction as an allergy.

Intolerance refers to a non-immune system reaction to certain food or substances, often involving digestive issues rather than an immune response. Infection involves the invasion of the body by pathogens, such as bacteria or viruses, leading to illness, and does not relate to sensitivity reactions to harmless substances. Deficiency typically pertains to a lack of nutrients or essential substances required for health, not relating to reactions toward benign stimuli.