It is not wrong to say that there are no application standards or best practices in balneotherapy considering traditional applications. There is not enough information about how changes in body temperature, duration, and frequency of exposure to heat affect therapeutic outcomes of balneotherapeutic applications. Body core temperature (BCT) is probably the best parameter for expressing the heat load of the body and can be used to describe the causal relationship between heat exposure and its effects. There are several reasons to take BCT changes into account; for example, it can be used for individualized treatment planning, defining the consequences of thermal effects, developing disease-specific approaches, avoiding adverse effects, and designing clinical trials. The reasons why BCT changes should be considered instead of conventional measures will be discussed while explaining the effects of balneotherapy in this article, along with a discussion of BCT measurement in balneotherapy practice.