Introduction

The movement of beautiful and healthy hair, in addition to the luster and color tone, has a great impact on the impression of appearance and is becoming increasingly important, especially in today's world where people have more opportunities to express themselves through video content such as Social Networking Service. It has been reported that the swinging of hair tends to decrease with aging and hair damage^1,2. It is believed that not only the outside of the hair but also the inside has a significant effect on such hair movement, but ingredients and treatment techniques to improve these conditions have yet to be discovered.
In view of this, we focused on the medulla, a porous structure that exists in the core of hair, and developed Hair Medulla Care (HMC), a technology that enhances the permeability of various substances thereby allowing specific ingredients to act on the medulla^3,4. With this technology, we have already succeeded in enhancing the transparency of hair³ and displaying hair color more vividly⁴.
In this study, we investigated the effect of oil penetration on hair movement, focusing on the fact that HMC treatment enhances the penetration of oil-based ingredients. Through various investigations, we found that with HMC-treated hair, the penetration of cholesterol, the content which decreases in hair due to aging and damage⁵, induced less damping of oscillation by the hair giving it a beautiful and whippy movement that lasted longer as compared to untreated hair. From this, it is clear that the HMC technology not only provides static beauty in terms of luster and color tone, but also provides beautiful and healthy "swinging hair".

Materials and Methods

HMC was processed in the same way as in previous studies, consisting of liquid A and B^3,4. Cholesterol penetration was performed by immersion in liquid isoparaffin solution dissolved in cholesterol and rinsing with water between treatment with solution A and B.
Cholesterol permeability evaluation
Fluorescence-labeled cholesterol, TopFluor Cholesterol, was used to observe the above treated hair sections under a fluorescence microscope.
Observation and analysis of free oscillation of hair
The observation of free oscillation was performed following previous studies^1,2. The roots of the above-treated hair bundles were fixed, and the hair tips were lifted and oscillated to a horizontal position. The results were photographed. The natural frequency and the logarithmic decrement were calculated by tracking a marker attached to the center of the hair tip.

Results

Cholesterol permeability evaluation
Penetration of fluorescence-labeled cholesterol into the cuticle was observed in the non-HMC-treated hair, whereas the penetration into as far as the cortical CMC and medulla was observed in the HMC-treated hair.
Observation and analysis of free oscillation of hair
The cholesterol permeation-treated hair bundles showed a significant decrease in the logarithmic decrement and increase in natural frequency compared to untreated hair and continued to swing longer without decay. At both ends of the oscillation, the hair was observed to writhe.

Conclusion

In this study, we demonstrated that HMC treatment can dramatically enhance the penetration of cholesterol into the hair to replenish its content. In addition, we suggested that the treated hair could be transformed into "swinging hair," which is soft, well-wrinkled, and oscillation-resistant, and could improve the deterioration of hair movement due to aging and damage. Consequently, HMC technology has established a new approach to hair beauty by laying an emphasis on the movement of beautiful and healthy hair. HMC technology, the use of which results in hair that looks good from all angles, is expected to be applied to various cosmetics for scalp hair in the future.

References

1)E. Schulze zur Wiesche, et al. The swinging behaviour of human hair: a novel method to quantify hair collective movements, 23rd IFSCC Conference(2015)
2)L Bechthold, et al. Morphological Changes of Human Hair Related to “Graying”, J. Cosmet. Sci. Sep/Oct 2018;69(5):335-346.
3)T Mannari, et al. A Novel Concept “Hair Medulla Care” -Unveiling hair medulla structure can change grey hairs appearance-, 31st IFSCC Congress(2020)
4)T Hirayama, et al. A new approach to obtain attractive hair “Hair Medulla Care”, 26th IFSCC Conference(2021)
5)K. Nishimura, et al. Interrelationship between the hair lipids and the hair moisture, J. Jpn. Cosmet. Sci. Soc. 13,134-139(1989)