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

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.

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).

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.

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.

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