The human body is covered in fine, soft hair often referred to as “peach fuzz.” This subtle hair is distinct from the more noticeable strands found on the head or in other specific areas. It is present across large portions of the skin. This hair serves various biological purposes.
Understanding Vellus Hair
The scientific term for the fine hair commonly known as “peach fuzz” is vellus hair. This type of hair is characterized by its very fine texture, short length, and minimal pigmentation. Vellus hair typically measures less than 2 millimeters long and has a diameter around 0.03 millimeters, making it considerably thinner than other hair types. It often appears colorless or very light due to a lack of melanin, the pigment that gives color to hair and skin.
Vellus hair covers most of the human body, including the face, arms, legs, and torso. However, it is not found on certain areas such as the palms of the hands, the soles of the feet, the lips, or parts of the external genital regions. It develops during childhood, replacing a thicker fetal hair called lanugo hair.
Vellus Hair vs. Terminal Hair
Vellus hair stands in contrast to terminal hair, which is the thicker, longer, and more pigmented hair found in other body regions. Terminal hair is prominent on the scalp, eyebrows, and eyelashes. After puberty, terminal hair also develops in areas like the armpits, pubic region, and on the face for males, forming beards.
A key structural difference is the presence of a medulla, a central core, which is typically found in terminal hair but absent in vellus hair. Terminal hair follicles are also larger and extend deeper into the skin compared to those that produce vellus hair. Terminal hair can grow significantly longer, with scalp hair potentially reaching up to 3 feet in length.
Function and Changes of Vellus Hair
Vellus hair serves several biological functions, primarily contributing to thermoregulation. It helps insulate the body by trapping a layer of air close to the skin, which assists in maintaining body temperature. Additionally, vellus hair aids in the evaporation of sweat, distributing it across the skin surface to facilitate cooling. These fine hairs are also connected to nerve endings, allowing for sensory perception, such as detecting light touch or air movement.
Vellus hair can undergo significant transformations, particularly during puberty. Increased levels of hormones called androgens cause vellus hair in certain areas, such as the armpits, pubic region, and male facial areas, to convert into coarser, darker terminal hair. While this transformation is a normal part of development, hormonal imbalances, such as those seen in conditions like polycystic ovary syndrome (PCOS) or Cushing syndrome, can also influence vellus hair density or its conversion to terminal hair. Conversely, in conditions like male pattern baldness, terminal hair on the scalp can miniaturize and revert to a vellus-like state.