Hair Therapy & Transplantation
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Fascinating Role of Vellus Hair in Human Physiology and Its Impact on Body Temperature and Skin Care

Reimold Philipp^{* *}Correspondence: Reimold Philipp, Department of Trichology, Omdurman Islamic University, Omdurman, Sudan, Email:

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Description

When it comes to body hair, most people are familiar with the coarser, darker terminal hair that grows on the scalp, underarms and pubic areas. However, there is another, less noticeable type of hair that covers much of the human body-vellus hair. Often overlooked in discussions about hair growth, vellus hair plays a significant role in the functioning of our skin and overall health. From its unique characteristics to its essential physiological roles, understanding vellus hair can provide fascinating insights into human biology.

Vellus hair is the fine, soft and usually light-colored hair that covers much of the body, with the exception of certain areas like the palms of the hands, soles of the feet and lips. Unlike terminal hair, which is thicker and darker, vellus hair is typically barely visible to the naked eye and it often lacks the pigmentation that gives terminal hair its darker color. Vellus hair is most noticeable on the face, particularly on the forehead, cheeks and upper lip, though it can also be found on the arms, back, chest and legs. On average, humans have around 5 million hair follicles, with a majority of them producing vellus hair.

Growth cycle of vellus hair

Like all types of hair, vellus hair goes through a growth cycle consisting of three distinct phases: anagen (growth), catagen (resting) and telogen (shedding). Vellus hair typically has a shorter anagen phase compared to terminal hair, meaning it grows more slowly and does not reach the same length. This is why vellus hair remains short, fine and often less noticeable than other types of hair.

Interestingly, vellus hair can undergo a transformation under certain conditions. In response to hormonal changes-such as those occurring during puberty, pregnancy, or the use of certain medications-vellus hair can be converted into terminal hair. This process is most evident in areas like the face and underarms, where the presence of more terminal hair becomes noticeable. Conversely, the reverse can also happen: terminal hair can regress into vellus hair due to aging or hormonal imbalances, a phenomenon seen in conditions like androgenetic alopecia (commonly known as male or female pattern baldness).

Functions and importance of vellus hair

While vellus hair may not always be the focal point of beauty or grooming discussions, it serves several important functions in maintaining the health and well-being of our skin. Here are some of its key roles:

Thermoregulation: Vellus hair helps regulate body temperature by acting as a protective barrier that traps a layer of air close to the skin. This layer of air provides insulation, helping to keep the body warm in cooler temperatures.

Protection and sensory function: Vellus hair also serves a protective function. The fine texture of vellus hair helps to shield the skin from dust, debris and harmful microorganisms. Additionally, vellus hair enhances the skin’s sensory abilities, as the hair follicles are connected to nerve endings.

Regulation of sebum production: Sebaceous glands, which are connected to hair follicles, secrete sebum (an oily substance) that helps keep the skin moisturized and lubricated. The presence of vellus hair helps facilitate the distribution of sebum across the skin’s surface, keeping it hydrated and preventing dryness or flakiness. This helps maintain the skin’s overall health and appearance.

Vellus hair and health conditions

In some cases, abnormalities in the growth or distribution of vellus hair can indicate underlying health conditions. For instance, excessive growth of vellus hair in women, a condition known as hirsutism, can be a sign of hormonal imbalances, such as polycystic ovary syndrome (PCOS) or certain endocrine disorders. In these cases, vellus hair may grow in areas where terminal hair is typically found, such as the chin, upper lip, or chest.

Conversely, the loss of vellus hair can be indicative of certain health problems, such as malnutrition, thyroid disorders, or alopecia areata. When the hair growth cycle is disrupted, vellus hair may either shed prematurely or fail to grow altogether, leading to noticeable changes in the texture and density of the skin.

Conclusion

Vellus hair may not command the same attention as the thicker, more visible terminal hair, but it is a vital component of our skin’s structure and function. From thermoregulation to sensory perception, vellus hair plays a role in maintaining our skin’s health and appearance. Whether serving as a barrier against environmental elements or helping to distribute oils to keep the skin smooth, vellus hair is far more significant than its inconspicuous nature might suggest. Understanding this subtle yet essential aspect of our biology not only deepens our appreciation of the human body but also underscores the complexity of the processes that keep us healthy and comfortable in our everyday lives.