Fever in children.

True fever occurs when there is an upward displacement of the thermostatic mechanism of the anterior hypothalamus in response to exogenous pyrogens. Fever may increase immune system activity, but it also induces an array of discomforts. In children under three months of age, fever is often an indication of serious illness, and aggressive evaluation is indicated. Febrile children aged three months to two years frequently do not manifest the classic signs and symptoms of specific diseases.