lanugo

mammalian hair

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Last updated

June 30, 2026

Quick Summary

Lanugo is a term for a dense, cottony growth of hair, specifically the soft, woolly hair that covers the fetus of some mammals. In humans, lanugo is the first type of hair to develop, appearing around the third or fourth month of fetal life. This downy hair is typically shed before or shortly after birth.12

Mammalian hair, in general, grows from the outer layer of the skin and serves various functions, including insulation against cold, camouflage, and sensory input (as with whiskers). The structure of hair consists of a shaft above the skin and a root below, made primarily of keratin.2

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…first to develop is the lanugo, a layer of downy, slender hairs that begin growing in the third or fourth month of fetal life and are entirely shed either before or shortly after birth. During the first few months of infancy there grow fine, short, unpigmented hairs called down hair,…
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…first to develop is the lanugo, a layer of downy, slender hairs that begin growing in the third or fourth month of fetal life and are entirely shed either before or shortly after birth. During the first few months of infancy there grow fine, short, unpigmented hairs called down hair,…
Read More