Vellus HairEdit
Vellus hair is the fine, short, pale hair that covers much of the human skin. It differs from terminal hair, which is coarser, longer, and usually pigmented. In adults, vellus hair is the predominant type over much of the body surface, contributing to a subtle, almost invisible layer that can become more apparent when hair is shed or the skin is examined closely. The term vellus comes from Latin, meaning “a fleece,” which reflects its light, wispy appearance. For many people, these hairs perform modest roles in tactile sensing and in maintaining a light barrier on the skin, though they are not a major factor in warmth or protection in the way thicker, pigmented hair can be.
Vellus hair is found on most of the body except for the palms, soles, lips, and parts of the genitalia, where hair is notably sparse or absent. The density and distribution of vellus hair vary by region, age, and individual genetics. In general, the limbs and trunk carry higher densities of vellus hair than specialized sites like the face in early childhood, though puberty can shift the pattern in some regions by transforming or replacing hairs with different textures.
Anatomy and distribution
Vellus hair originates from small hair follicles associated with sebaceous glands and a minimal arrector pili muscle. The hair shaft itself is very fine, often colorless or lightly pigmented, and lacks the thick cortex and medulla that characterize terminal hair. The follicle’s structure in vellus hair is comparatively small, which contributes to the hair’s light appearance and short apparent length.
Pigmentation in vellus hair is typically low because melanin production in the hair shaft is reduced relative to terminal hair. This ecological trade-off—light color with limited pigment—helps keep the skin’s surface looking even and reduces the visual impact of these hairs in most individuals. The distribution pattern of vellus hair aligns with the skin’s regional biology and is influenced by underlying genetics and hormone signaling. For readers curious about how hair forms, see hair follicle and keratin as structural anchors, and consider how pigment biology relates to melanin.
Development and growth cycles
Hair grows through a cycle that includes anagen (growth), catagen (transition), and telogen (resting) phases. Vellus hair generally has a relatively short or less robust anagen phase compared with many terminal hairs, and its cycles can be shorter, slower to lengthen, or more variable depending on site and physiology. The cycle continues with shedding and renewal, so vellus hair can seem to appear or disappear over time without dramatic changes in overall skin health.
In some conditions, hairs that begin as vellus can transition toward a thicker, more pigmented form—a process known as miniaturization when influenced by hormones or disease processes. In the scalp, for example, androgen-driven mechanisms can cause terminal hairs to shrink and adopt a vellus-like morphology in areas affected by androgenetic alopecia, reducing visible density. See androgen and androgenetic alopecia for related regulatory and clinical contexts. For broader context on hair cycles, refer to anagen, catagen, telogen, and exogen.
Regulation, variation, and clinical relevance
Multiple factors influence vellus hair density and appearance, including hormones, genetics, age, nutrition, and environmental factors. Androgens promote the growth of certain terminal hairs in some body regions, while other sites may maintain vellus characteristics under typical hormonal conditions. Aging tends to alter hair density and texture, often reducing the prominence of some terminal hairs and leaving vellus hairs more noticeable in certain areas. When hair loss or changes in density are a concern, clinicians evaluate patterns that may involve vellus-to-terminal transitions or miniaturization in susceptible regions. See hormone, androgen, and alopecia for related discussions.
Disorders affecting vellus hair are usually discussed in the broader context of hair biology, including conditions like alopecia and hirsutism (which describes excessive terminal hair growth in women in certain areas). While these topics intersect with vellus hair in terms of growth cycles and follicle behavior, the clinical emphasis often centers on overall hair density and texture rather than the fine hairs alone. See also hair for a general overview of body hair types and terminal hair for the coarser counterpart to vellus hair.