Articles. Hair Colorist Los Angeles Hair Color Trends. HairBoutique.com. Hair Dyes and Hair Treatments - Chemistry Encyclopedia - structure, reaction, water, proteins, metal, number, salt. Hair has no vital function in the human body but provides an outward sign of health and social communication. The history of hair coloring dates from ancient dynasties of Egypt and China where mineral and plant dyes were widely available to cosmeticians. Through the ages, women in particular have dyed their hair to hide grayness and to improve their appearance.
General Features of Hair In all mammals, hair develops as an epidermal structure from papillae deep in the skin and acquires characteristic patterns on the scalp, eyebrows, eyelashes, and elsewhere on the body. In humans, hair growth is continuous throughout life (declining with advancing age), occurs in cyclic patterns, and Figure 1. is influenced by androgens , thyroid hormones, and dietary factors. Chemically, human hair contains approximately 85 percent protein, 7 percent water, 3 percent lipid , 4.7 percent protein-bound sulfur (as cystine), and low concentrations of trace minerals (e.g., iron, zinc, copper). Table 1.