Background Sensory and structural characteristics of hair can be modified by chemical and physical treatments, as dyeing, brushing, but also by external factors, as sunlight radiation. However, quantitative data relating damage to the degree of hair curliness and treatments are missing. Objective To evaluate the effect of chemical and physical treatments on different types of hair. Methods In this study, we compared the effects of bleaching/dyeing, thioglycolate‐based straightening, brushing/flat iron and UVA/Vis radiation on different types of hair: Caucasian (straight dark brown, straight blond, wavy dark brown and curly dark brown) and Afro‐ethnic hair. Results Bleaching/dyeing and UVA/Vis radiation increased combing work of Afro‐ethnic hair tresses, indicating damage to the cuticle scales, which was confirmed by SEM images. Further, bleaching/dyeing caused wear on cuticles with high protein loss and reduction on the tryptophan content, independently of the hair curliness, which characterizes those procedures as very aggressive to hair structure. Straightening using ammonium thioglycolate, due to the oxidative treatment evolved, caused significant colour fading in brown/black tresses, while UVA/Vis radiation affected the colour of only blond hair tresses since they are poor in eumelanin, the photoprotective and photostable melanin molecule. Conclusion The combination of analytical and image techniques contributed to understanding how the hair shape is related to the type of damage caused by several chemical and physical treatments. These findings contribute to the development of safety cosmetics that insure the beauty of curly hair, both Caucasian and Afro‐ethnic hair.

lower charge density polymer yields higher tress stiffness than the higher charge density polymer at 50% RH, but this trend is reversed at 90% RH. A hypothesis is offered in explanation of this phenomenon, relating adhesion and cohesion to the performance of fixative-hair composites. At high humidity, moisture can plasticize the polymers, reducing the cohesive strength, so electrostatic attraction and thus adhesion becomes the dominant force. Evidence to support this hypothesis is given.

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Hair damage is caused by several chemical and physical factors. Each kind of damage affects different parts of the hair structure (cuticle and cortex) and may be noticed differently by consumers. This work aimed to assess how trained panelists perceived several types of damage to different hair types. Therefore, we prepared wavy and tight curly tresses and submitted them to standardized chemical and physical damages. A trained panel performed sensory analyses of the damaged tresses compared to virgin hair. In the analysis, the panelists assessed eight different sensory attributes: glow, silkiness, smoothness, dryness, combability, volume, frizz, and balance. The results showed that damage from UV exposure most affected the sensory attributes of hair tresses. Hair treatments that promote fiber alignment (straightening and thermal damage) had “hidden” harmful effects and attributes were noticed as if hair had improved. Practical Application Consumer's hair suffers damage daily from many sources. Most previous studies have reported the results of instrumental assessments of these damages, without considering how they are perceived by people. The current study assessed how panelists noticed hair damage from different sources to better understand damage from the consumer's point of view.