Fever is a state of elevated core temperature that is frequently, but not always, a component of the defensive responses of multicellular organisms (host) to the invasion of live (microorganisms) or inanimate matter recognized as pathogenic or alien by the host. Fever is one of the earliest clinical indications of disease in the mammalian host and one of the leading causes of medical consultations globally. The endocrine, neurological, Immunological, and behavioral systems that control the multi-systemic effects of the febrile response may be responsible for its complexity. In addition to a controlled rise in body temperature, fever is also accompanied by a variety of illness-related behaviors, modifications to the physiological and metabolic makeup of many bodily systems, and changes to immunological responses. Fever of unknown origin (FUO) is defined as fever & more than 101 °C Lasting for 3 weeks or more for which no cause is apparent After 1 week of outpatient investigation. A practical definition is fever & more than 101 °F measured on several occasions over a 7-day period. Febrile illness in children is a major concern to the parents and requires prompt intervention. The conventional treatment has ill effects since it uses many drugs to treat the illness and it is also not favored by the child. But homoeopathic management treats the same illness with a single, minimal dose medicine and is also easily consumed by the child which makes it children friendly. The purpose of this study is to effectively manage pyrexia of unknown origin in children using therapeutics of fever by H.C.Allen.