Effects of ultraviolet rays and particulate matter on hair porosity in damaged hair

Abstract Background With growing interest in hair health, researchers are exploring aspects beyond the surface qualities of hair, such as its porous inner structure. While previous studies have focused on the effects of treatments such as perming and hair dying on hair porosity, less emphasis has been paid to the effects of harmful environmental factors such as ultraviolet (UV) rays and particulate matter on the porous nature of hair. Aims The aim of this study was to bridge this gap by investigating how UV rays and particulate matter affect hair porosity in different ways. Our study could help elucidate how these external factors influence hair health and shed light on previously unknown aspects of hair porosity. Methods Hair tresses were bleached, cut into 1 cm‐long sections, and stained with methylene blue. The sections were then irradiated with UV light or exposed to particulate matter. Results Bleached hair absorbed more methylene blue than normal hair. UV radiation‐induced hair porosity occurred at 3 h after irradiation and increased with time. Particulate matter alone did not affect the porosity of the damaged hair; however, in combination with UV irradiation, it substantially increased hair porosity. Conclusion Environmental challenges such as a depleted ozone layer and increasing pollution may increase hair porosity, which can be prevented by maintaining healthy hair.