不明原因发热是指医师在诊疗过程中根据患者的临床信息均未能找到发病原因的疾病。目前，该疾病已成为医学界非常棘手的难题。西医学认为，不明原因发热的发病机制尚不明确，且临床化验和检查结果均为阴性，为临床工作不能提供有效信息，因此，在治疗上主要以退热为主。而在中医学领域，可通过中医辨证论治、四诊合参根据患者的症状及体征予以辨证用药。就不明原因发热而言，中医药治疗不是一味的使用退热剂，而是根据患者的寒热虚实予以不同的治疗原则。而和解少阳法对治疗表证未解，邪热入里，正邪相争于半表半里之间，邪扰少阳引起的不明原因发热疗效显著。

Fever of unknown origin (FUO) is a disease whose causes remain unknown according to the pathients′ clinical information. Nowadays, FUO becomes a hard nut to crack. For modern medicine, the pathogenesis of FUO has not been found, and the results of clinical examinations are negative, so the therapies of FUO are often symptomatic treatment. However, in traditional Chinese medicine, we can apply kinds of therapies to treat FUO by syndrome differentiation and comprehensive analysis of data gained by four diagnostic methods. For FUO, we can not only use defervescent drugs in traditional Chinese medicine, but use different treatments according to cold, heat, deficiency or excess. Reconciling shaoyang is an effective therapy for FUO when exterior syndromes don′t relieve and the interior syndromes invade the organism.