What is a substance that can initiate a fever called?

A substance that can initiate a fever is called a pyrogen. Pyrogens are typically substances that provoke an inflammatory response in the body, leading to an increase in body temperature. This is often a natural part of the body’s defense mechanism against infections and diseases, helping to enhance immune functions and creating an environment that is less favorable for pathogens.

In contrast, antipyretics are agents that reduce fever, while analgesics relieve pain. Antibiotics are used to treat bacterial infections but do not directly relate to the process of inducing fever. Understanding these definitions clarifies the role each of these substances plays in the body's physiology and pharmacology.