June 22, 2018

Mandom Discovers that “Basic Blue 124” Dyes Hair but DoesNot Easily Dye Skin: Applying this Finding to the- Development of Hair Color Conditioners Mandom Corporation (Headquarters: Osaka; President Executive Officer: Motonobu Nishimura; hereafter,Mandom) has been involved in the development of hair color products that are comfortable to use.
One type of hair color product is the at-home, low-hassle “hair color conditioner.”*1 Basic dyes*2 are used in haircolor conditioners. However, increasing the amount of dye to heighten dyeing power causes skin to be dyed as well,which has long been a problem with these products. We have found that a certain basic dye, Basic Blue 124, has thespecial characteristic of coloring hair without coloring skin. Because Basic Blue 124 does not dye skin, we can increase
its use in our products. As a result, hair color conditioners into which Basic Blue 124 has been incorporated will maintaintheir color hold while requiring less time to set than existing products.
1. The Search for Dye that Colors Hair but Does Not Easily Color Skin
Several types of dyes are used in cosmetic gray hair dyes, but in hair color conditioners, basic dyes are one of themost frequently employed types. Among basic dyes, selection of blue-colored dyes is especially important because theyeffectively darken hair. However, if too much blue dye is incorporated into a product, it begins to dye not only hair, butalso the skin of the hands and face.
Thus, we focused on the hydrophobicity of the skin, assuming that highly hydrophilic dyes would not easily
permeate the skin. We began to search among the dyes that meet our safety standards for one with particularly highhydrophilicity. As a result, we discovered that Basic Blue 124 dyes hair but does not easily dye skin—any dyeing of theskin can easily be washed out (Figure 1).
2. Evaluation of Hair and Skin Permeability of Basic Blue 124
We evaluated the permeability of hair to the dye by making an oblique cross-section of dyed hair and examining itwith an optical microscope (Figure 2). After examination, we discovered that Basic Blue 124 had permeated the surfaceof the hair and nearby regions in the same way that the blue dyes in our existing products do.
We evaluated the permeability of skin to the dye by vertically sectioning cultured skin whose surface had been
exposed to dye and examining it with an optical microscope and TOF-SIMS*3 (Figure 3). We found that, compared tothe blue dyes incorporated into our existing products, Basic Blue 124 did not permeate the inner layers of the skin.

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-1-3. Applying Basic Blue 124 to Our Products
We developed a test hair color conditioner that takes advantage of Basic Blue 124’s high hair permeability and low
skin permeability and compared this test product with our existing products. We found that, while our existing products
required a setting time of 5 minutes, setting the test product for only 3 minutes did not affect its dyeing power andprevented it from dyeing the skin (Figure 4).
In the future, we will continue to implement Basic Blue 124 in our products and develop hair color products that
consumers can use comfortably and safely; we plan to do this through continuously advancing our technology. Notes:*1 A cosmetic product used as a hair conditioner that gradually decreases the noticeability of gray hairs. It isapplied after using shampoo, allowed to set for a few minutes, and then washed out.
*2 Dyes that have positive charge; they have the ability to dye the surface of the hair and surrounding areas.
*3 TOF-SIMS (Time-of-Flight Secondary Ion Mass Spectrometry)An analytical method in which a sample is irradiated with an ion beam and ions emitted from the sample surface
are detected, allowing the presence of the target molecule to be identified. Substances with masses close to thatof the target molecule on the sample surface may appear as noise.
[Reference Materials]
Figure 1: Comparison of Basic Blue 124’s Dyeing Power and Dye in Existing Products
Dyeing power (bundle of human gray hair) and skin staining (after washing with soap)
Dyeing power (bundle of human gray hair)

Skin staining (after washing with soap)

Basic Blue 124

Blue dye contained in our
existing products

Figure 2: Evaluation of Dye Permeability into Gray Human Hair (Optical Image)
Basic Blue 124

Oblique cross-section

Blue dye contained in ourexisting products-2-Figure 3: Evaluation of Dye Permeability into Cultured Skin (Examination of Cross-Section)
TOF-SIMS (Ion mapping)
Optical Image

Basic Blue 124 Blue dye contained in our existing products

Before dyeing(:m/z344.2)(:m/z270.1)

Before dyeing

Basic Blue 124

After dyeing

Noise from culturedskin

Blue dye contained inour existing products
Dye permeation*Basic Blue 124-specific m/z 344.2 was detected from cultured skin before dyeing. And after dyeing with BasicBlue 124, the same distribution (no concentration gradient from the surface) was observed, indicating that this isnoise from the cultured skin.

Figure 4: Comparison of Dyeing Power of Test Product and Existing ProductDyeing power (bundle of human gray hair) Skin staining (after washing with soap)

Test product containing
BasicBlue 124 (3-minute set)

Existing product(5-minute set)

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