The present review showed the importance of using the differential scanning calorimetry (DSC) in the evaluation of the hair damage. Many hair-straightening treatments necessarily involve a heating process, which even at low temperatures can cause damage to hair. Several researches demonstrated the influence of the exposure to heat in various types of hair, correlating it with the increase in the temperature. In this sense, the importance of this research is in raising awareness to the consumers and professionals (cosmetic formulators, researchers, hair stylists and dermatologists) about the issues of employing heat in the modification of the hair. To this, the present review refers to a broad and updated bibliographic collection comprising several studies related to the investigation of the thermal events that occur in the hair under heating until 300 C, including the denaturation of the a-keratin, employing DSC. This protein forms a crystalline structure in the hair cortex and provides the hair mechanical properties such as strength and elasticity. But once denatured, the damage done to the hair may be irreversible. However, studies related to thermal decomposition of this protein are necessary due to the increased use of thermal hair styling tools, which can be associated, or not, with chemical treatments. Yet, in the literature, few reviews on this important tool of characterization and evaluation in hair samples are available. Thus, additionally, the objective of this work is to support researchers to direct the study with most feasible experimental conditions to achieve more potent results employing DSC.