**2. Anatomy and physiology of facial hair**

*1.2.5. The middle ages [3]*

or " The Mister" in Arabic. (Figure 3). [11]

588 A Textbook of Advanced Oral and Maxillofacial Surgery Volume 2

**Figure 3.** Charles IV, Holy Roman Emperor.

require it or those who are in academia.

**1.3. Modern prohibition of beards [3]**

In the middle ages, the beard had still an important role, figure 3 depicts the picture of El Cid

While most noblemen and knights were bearded, the Catholic clergy were generally required to be clean-shaven. This was understood as a symbol of their celibacy. By the early 20th century beards began a slow decline in popularity. Although retained by some prominent figures who were young men in the Victorian period (like Sigmund Freud), most men who retained facial hair during the 1920s and 1930s limited themselves to a moustache or a goatee (such as with Marcel Proust, Albert Einstein, Vladimir Lenin, Leon Trotsky, Adolf Hitler, and Joseph Stalin). In America, meanwhile, popular movies portrayed heroes with clean-shaven faces and "crew cuts". Concurrently, the psychological mass marketing of companies like Gillette popularize short hair and clean shaven faces as the only acceptable style for decades to come. Those who grow beards are frequently either old, Central Europeans, members of a religious sect that

Professional airline pilots are required to be clean shaven to facilitate a tight seal with auxiliary oxygen masks. Similarly, firefighters may also be prohibited from full beards to obtain a proper seal with equipment. This restriction is also fairly common in the oil and gas industry for the same reason in locations where hydrogen sulfide gas is a common danger. Other jobs may prohibit beards as necessary to wear masks or respirators. [12] Isezaki city in Gunma, Japan,

Human hair has been categorized into three ethnic groups according to distinguishable characteristics: Asian, Caucasian, and African hair. These ethnic groupings show distinct characteristics in hair density, diameter, shape, mechanical properties and composition. [15]

The hair follicle itself determines the appearance of the hair. The typical hair follicle of Asian hair is round (Figures 4 and 5), whereas those of Caucasians and Africans are ovoid and elliptical, respectively. [16]

The shape of the hair follicle is thus believed to contribute to the appearance and the geometry of the hair. Asian hair has a circular geometry, African hair has an elliptical shape, and hair of

**Figure 5.** Asian beard hair, note the different contour of the beard hair from scalp hair, reprinted by permission of The Society of Cosmetic Chemists

Caucasians is of an intermediate shape. The chemical and protein composition of hair does not vary across ethnic groups, and there is no difference in the keratin types. However, African hair generally has less tensile strength and breaks more easily.
