Which of the following is a symptom of a pyrogenic reaction?

A pyrogenic reaction is characterized by an increase in body temperature, commonly resulting in fever. This type of reaction often occurs in response to the introduction of pyrogens, which are substances that induce fever, typically due to the presence of bacteria or other foreign materials in the body.

Fever is a physiological response that helps the body fight infection, and it is one of the most recognized symptoms linked to pyrogenic reactions. The process involves the hypothalamus raising the body's set temperature in response to pyrogens, leading to increased heat production and decreased heat loss, which contribute to the overall feeling of warmth and the physical manifestation of a fever.

Dry mouth, fatigue, and anemia, while they may occur for various reasons, are not direct indicators of a pyrogenic reaction. Therefore, fever stands out as the specific and primary symptom associated with this type of reaction, confirming why it is the correct answer.