According to Kao, more than half of some 1,400 survey respondents expressed concern or slight concern as to whether scalp cleanliness continues to the next day and after shampooing. Of those, more than 40% felt cleanliness was indicated by the smooth, dry feeling of hair.
Furthermore, regarding the cause for feeling less clean, dirt such as dust was the most frequently chosen answer, accounting for more than 60% of responses. As such, Kao researchers examined how fine dirt particles such as dust and pollen from the external environment adhere to hair—and what they could do about it.
Cedar pollen was used as a representative particle. During a period from March to April 2019, a hairpiece, hair bundle and clothes were placed outside in the Tochigi Prefecture, Japan, air for a few hours each day and the amount of cedar pollen antigen attached to each sample was quantitatively determined using ELISA.
Furthermore, hair collected from the bundle was treated with gentian violet staining protein and observed under a light microscope. Spherical particles were stained blue, thus confirming the adhesion of pollen to individual hairs. Interestingly, a comparison of allergen quantity per unit area revealed the amount adhering to hair was equal to or greater than that adhering to clothes.
Oil Adhesion and Test Formulas
Based on these findings, it was speculated one of the causes for hair contamination by fine particles was the presence of oil. As a follow-up, technologies for controlling oil on hair were examined for dirt-shielding effects.
In reference to sebum, a shampoo and conditioner were formulated and silicone-blended for improved texture. For reducing liquid-state sebum on the hair surface, various oil absorbent substances were screened. Cationized hydroxypropylcellulose (C-HPC), in particular, was blended into the test shampoo.
Twenty hours after shampooing, the coefficient of static friction, a parameter crucial to the adhesion of fine dirt particles, was significantly suppressed, as compared to a formula without the compound. For the test hair conditioner, results indicated the use of low-viscosity silicone was sufficiently effective.
From the initial findings, test subjects used the proposed test shampoo and hair conditioner in combination for six days on only one side of the head. Hairs were then collected and exposed to white-colored fine particles to evaluate changes in color. Results revealed the adhesion of fine dirt particles was significantly inhibited by use of the test products
Results of these studies first confirmed the attachment of fine dirt particles, such as pollen and dust. In addition, they revealed the effectiveness of a dirt shield system incorporating a shampoo blended with C-HPC followed by the use of hair conditioner including silicone to optimize viscosity.
According to the company, the findings obtained in this study will be used for future hair care product development. These findings were first presented at the Annual Meeting of the Society of Fiber Science and Technology in 2019.