Analysis of Hair Coloring

History of Hair Dye

Hair coloring is not a new practice; people have been changing their hair color since the era before Christ (1). The Romans had a preference to dark hair, and to fulfill this desire, they used boiled walnuts together with leeks to create the dye. They also used henna, sage and indigo plants to darken their hair (2). Ancient Greeks believed that blonde hair represented honor and courage and that is why men dyed their hair with harsh soaps and bleaches (3). During the Renaissance, blonde hair was considered appealing, so women would mix black sulphur, alum and honey to lighten their hair in the sun (2). In 1907, French chemist Eugene Schueller discovered the first synthetic hair dye with a new chemical called paraphenylenediamine. After his discovery, he founded the French Harmless Hair Dye Company, which the name then became L’Oreal (4).

General Features of Hair

1. Hair Anatomy

Human hair is a tissue that contains keratins that are insoluble proteins composed of eight amino acids (5), which grows from the bulb of follicles stretching from the surface of the skin through the epidermis, and lastly to the dermis. The growth cycle of hair is controlled by the dermal papilla, located at the center of the bulb. Basal layers produce hair cells, and surround the bulb. The hair pigment is produced by melanocytes that are inside the bulb. Blood vessels close to the base of the bulb maintain the growth of hair. The growth of hair is a cycle with three stages t called, anagen, catagen, and telogen. During the first stage the hair fiber grows for two to six years. At the catagen stage, growth of the hair fiber slows down at the dermal papilla. The bulb shrinks and goes towards the epidermal surface and last for two to three weeks. At the last stage the growth stops, and a new bulb originates from under the shrunken bulb, where it eliminates the old hair fiber and produces a new one. It lasts for six to twelve weeks. Hair grows at more or less sixteen centimeters per year (6).

The terminal hair fiber has a circular cross section that shows three different regions, the cuticle, the cortex and the medulla. The cuticle is five to ten scale layers that overlap each other close to the scalp. Its main function is to protect the hair and as the hair grows through the skin, the scale edges are unbroken. The cortex has the major part of the hair fiber mass; it is around 90% of the weight of the dry hair. Its cells have helical proteins tightened in a matrix full of cystine cross-links, and are made of smaller filaments called microfibrils. The microfibrils have smaller filaments called protofibrils that are made of О±-helical proteins. Lastly, the medulla region only has a small portion of the fiber mass, and does not provide a known function. It has a porous that may be steady along the fiber axis, or it could be present or not in different spots of the fiber axis (6).

2. Chemical Composition of Hair

The Hair is composed of 45.2% carbon, 27.9% oxygen, 6.6% hydrogen, 15.1% nitrogen and 5.2% sulphur (5). There are four chemical components in human hair, minerals, pigments, lipid and proteins. Minerals that are found in human hair are, Ca, Mg, Sr, B, Al, Na, K, Zn, Cu, Fe, Au, Hg, Pb, Sb, Ti, W, Mo, I, P, and Se. These minerals arise from sweat, and the environmental elements that originate from cosmetics, water, and pollution. Hair pigments are located in the cortex and the medulla. There are two types of pigments, the brown-black melanin and the red melanin. Hair pigment is formed in the melanocytes, which it first produces amino acid tyrosine. The pigment granules are added to new cells close to the base of the bulb, which are going through keratinization. Hair Lipids are either free lipids or structural lipids. Free lipids exist on the surface and inside of the hair fiber, and it are responsible for oily hair. Lastly, the amount of proteins present in the hair depends on the level of humidity, if low humidity then the number of proteins are high, and vice-versa (6).

3. Natural Hair Color

Generally, hair color is black, brown, red or blond. The natural color of hair depends on ethnicity, but black is the most common hair color. The hair color changes as the age changes it first becomes grey and the white. This fact of life is one of the reasons many people dye their hairs (7).

Hair Dyes and Cosmetic Coloring

1. Categories of Hair Dye

There are three categories of hair dye, permanent, semi-permanent and

temporary.

Permanent Hair Dye:

Permanent