Having a hypersensitivity reaction to a substance is defined as which term?

• A. Having an infection.
• B. Having a hypersensitivity reaction to a substance.
• C. A lack of energy.
• D. A fever of unknown origin.

Answer: (B)

An exaggerated immune response to something harmless. When the body encounters a substance it misidentifies as a threat, it mounts a hypersensitivity reaction, which is the immune system reacting in an outsized way. This is the essence of the term described. The other options point to different problems—an infection involves pathogens, a lack of energy means fatigue, and a fever of unknown origin is a fever with no identified source. So the best term for this description is a hypersensitivity reaction to a substance.