New Discovery Targets Core of Complex Hair Damage: Finding of 'Ultra-Fine Voids' in Hair and Development of New Repair Technology Focusing on 'Moisture'

Hoyu Co., Ltd. (Headquarters: Nagoya City, Aichi Prefecture; Representative Director, President & CEO: Yoshihiro Sasaki; hereinafter 'Hoyu') has discovered that ultra-fine voids*1 are formed inside hair that has suffered complex damage from hair coloring and heat. As a result of research into care technology focusing on these ultra-fine voids, the company has established a new hair care technology that effectively repairs the voids by combining two specific ingredients*2. The company plans to apply this technology to future new products.

Background and Purpose of the Research

Amid the daily use of hair coloring and hair irons in recent years, our company has been researching the phenomena caused by the complex damage from these practices on hair. As damage progresses, hair with complex damage becomes non-uniform from root to tip, and its moisture environment is also disrupted, leading to issues with the reproducibility and sustainability of beautiful hairstyles.

When observing the interior of hair with complex damage using HV-TEM*3, we discovered the presence of ultra-fine voids, measuring several to several tens of nanometers, which are even smaller than conventionally known damage holes, near the cortex and cuticle. These voids increase in number according to the degree of complex damage (Figures 1 and 2). In other words, we confirmed that these ultra-fine voids are one of the causes of the aforementioned issues.

Results of the Research

In this study, we advanced research on technology to repair the ultra-fine voids present in the cortex. As a result, we identified two ingredients that effectively repair these ultra-fine voids.

These two ingredients have the property of binding to each other, reducing the ultra-fine voids (Figure 3) and increasing the proportion of bound water*4 inside the hair, thereby adjusting the moisture balance within the hair to a state closer to that of healthy hair. Furthermore, this technology for repairing ultra-fine voids inside the hair enables an approach to the interior of the hair, which has been difficult to repair until now, leading to beautiful hairstyles that are well-maintained from within the hair.

*1 Voids inside the hair measuring several to several tens of nanometers *2 Hydrolyzed collagen and ribose *3 High-Voltage Transmission Electron Microscope *4 Moisture in the hair that interacts with internal proteins/keratin and is less likely to be lost due to everyday damage

About Hoyu Co., Ltd.

Since its founding in 1905 (Meiji 38), Hoyu has been developing its business in hair color and hair cosmetics for both home and professional use. It boasts the No. 1 domestic market share in the retail hair color market*5 and has been engaged in the manufacture, sale, research, and development of hair color-related products for many years.

Having celebrated its 100th anniversary in 2023, the company continues to move towards the next 100 years without changing its attitude of constantly creating new things, such as actively expanding its business overseas and taking on challenges in the allergy field with a forward-looking approach to safety research.

*5 Survey period: INTAGE SRI Hair Color Market: January 1996 – December 2017, cumulative annual sales amounts INTAGE SRI+ Hair Color Market: January 2018 – December 2025, cumulative annual sales amounts

About the 'Genki Wakuwaku Vision 2030'

Hoyu has set forth the 'Genki Wakuwaku Vision 2030' and aims to create value from three perspectives – customers, the environment, and employees – to realize a sustainable society. Based on the corporate slogan 'COLOR YOUR HEART', this vision consists of the 'Customer Color Vision' to bring color to customers' lives, the 'Environment Color Vision' to reduce environmental impact and promote the 4Rs, and the 'Employee Color Vision' to create an environment where employees can be healthy in mind and body and feel motivated to work.

Hoyu Co., Ltd. Company Profile

Head Office: 501 Tokugawa 1-chome, Higashi-ku, Nagoya City, Aichi Prefecture Representative: Representative Director, President & CEO Yoshihiro Sasaki Founded: 1905 (Meiji 38) Established: 1923 (Taisho 12) Capital: 110 million yen Number of Employees: 1,080 (as of October 31, 2025) Consolidated Net Sales: 52.7 billion yen (fiscal year ending October 31, 2025) Domestic Production Bases: Seto Plant (106-2 Yamanota-cho, Seto City, Aichi Prefecture), Sakuragaoka Plant (985 Anada-cho, Seto City, Aichi Prefecture) Business Description: Manufacture and sale of hair color and hair cosmetics Website: https://www.hoyu.co.jp/