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2019/12/18

  • News Release
  • R&D

Adhesion of Fine Dirt Particles such as Dust and Pollen to Hair, and Development of Hair Shield Technology

This is an English translation of a news release in Japanese on November 25.

The Hair Care Research Laboratory of Kao Corporation (Michitaka Sawada, President) researched the characteristics of fine particles adhering to hair as a factor for degradation of hair texture the day after washing. Results of those investigations identified factors with effects on the adhesion property of dirt particles, such as dust and pollen, to hair. Furthermore, in consideration of the presence of liquefied oil*1 on hair as a factor that increases particle adhesion, a method for suppression of that by technologies included in shampoo and hair conditioner products was developed.
The findings of this study were presented at the Annual Autumn Meeting of the Society of Fiber Science and Technology in 2019 (Nagano Prefecture, Japan, November 9-10, 2019).

  • * 1 Sebum secreted from scalp that moves to hair roots and oil solution such as silicone contained in haircare products.

Background

According to a recent survey conducted by Kao, more than half of the respondents replied that they were ‘concerned’ or ‘slightly concerned’ regarding whether scalp cleanliness continues the next day after shampooing. Of those, more than 40% felt that cleanliness was indicated by a smooth and dry feeling when touching their hair.*2 Furthermore, regarding the cause for the “feeling of worsened hair cleanliness during the day in comparison to at the time of leaving home in the morning”, ‘dirt such as dust’ was the most frequently chosen answer, accounting for more than 60%.*3
In the present study, with focus on fine dirt particles originating from the external environment, such as dust and pollen, the characteristics of their adhesion to hair were investigated. Based on those findings, technology for suppressing such adhesion by daily use of shampoo and hair conditioner was developed.

  • * 2 Kao survey, December 2016, 1400 subjects
  • * 3 Kao survey, July 2016, 150 subjects

Study 1. Analysis of adhesion of fine dirt particles to hair in external environment

Cedar pollen, used as a representative of fine dirt particles, was examined in this study performed in Tochigi Prefecture. During the period from March to April 2019, a hairpiece, hair bundle, and clothes were placed outside in the air for a few hours each day (Fig. 1), then the amount of cedar pollen antigen (Cryj 1) attached to each sample was quantitatively determined using ELISA.
Hair collected from the bundle was treated with gentian violet staining protein and observed under a light microscope. Spherical particles were stained in blue and adhesion of pollen to individual hairs was confirmed (Fig. 2).

Fig. 1. Preparation of experimental samples for determining amounts of adhered pollen.

Fig. 2. Hair after exposure to outside air.

A comparison of allergen quantity per unit area revealed that the amount adhered to hair was equal to or greater than that adhered to clothes (Fig. 3).

Fig. 3. Amounts of cedar allergen attached to hair and clothes.

Study 2. Development of technology for suppressing adhesion of fine dirt particles, such as dust and pollen, to hair using shampoo and hair conditioner

Based on findings obtained in Study 1, it was speculated that one of the causes for hair contamination with fine particles is the presence of oil. In this study, technologies used for controlling oil on hair were examined for their dirt shielding effects. Regarding sebum, shampoo that washes the entire hair including the root and conditioner with silicone blended for improved texture of the formula were focused on for development.
For reducing liquid-state sebum present on the hair surface, various oil absorbent substances were screened. Cationized hydorxypropylcellulose (C-HPC), developed in the Kao laboratory, was blended into the test shampoo. At 20 hours after shampooing with that, elevation of the coefficient of static friction, a parameter for adhesion of fine dirt particles, was significantly suppressed as compared to without the compound.
For the test hair conditioner, the results indicated that use of low-viscosity silicone would be effective.

Based on these findings, subjects were instructed to use the test shampoo and hair conditioner in combination for 6 days on one side of their head. Black hairs were then collected and exposed to white-colored fine particles to evaluate change in color by 6 research staff members. Those results revealed that adhesion of fine dirt particles was significantly inhibited by use of the test products (Fig. 4).

Fig. 4. Inhibition of fine particle adhesion to hair using our newly developed technology.

Conclusion

Results of the present analysis regarding degradation of hair when exposed to the external environment showed attachment of fine dirt particles such as pollen. In addition, it was confirmed that dirt in the external environment became attached to hair at the same degree or more as to clothes when calculated based on unit area. The effectiveness of dirt shield technology by focusing on liquified oil on hair was also investigated. Those results confirmed that adhesion of fine dirt particles such as dust and pollen from the environment could be inhibited by daily hair washing with shampoo blended with an oil-absorbing polymer (C-HPC), followed by use of hair conditioner that included silicone to optimize viscosity.
The findings obtained in this study will be used for future development of hair care technology and formulation.

About Kao

Kao creates high-value-added products that enrich the lives of consumers around the world. Through its portfolio of over 20 leading brands such as Attack, Bioré, Goldwell, Jergens, John Frieda, Kanebo, Laurier, Merries and Molton Brown, Kao is part of the everyday lives of people in Asia, Oceania, North America and Europe. Combined with its chemical division, which contributes to a wide range of industries, Kao generates about 1,500 billion yen in annual sales. Kao employs about 33,000 people worldwide and has 130 years of history in innovation. Please visit the Kao Group website for updated information.

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