Final answer:
Inflammation is the fastest responder and most sensitive indicator of acute inflammation. It causes redness, swelling, and warmth. Skin testing with allergen extracts can detect the release of histamine and other mediators, resulting in a positive wheal and flare response.
Step-by-step explanation:
Inflammation is the fastest responder and most sensitive indicator of acute inflammation. It is a response of the innate immune system that establishes a physical barrier against the spread of infection and repairs tissue damage while causing redness, swelling, and warmth. When allergen extracts are injected into the skin, the release of histamine and other mediators leads to a positive result known as the wheal and flare response, which includes soft, pale swelling surrounded by a red zone.