Medical Definition of Hair, lanugal

  • Medical Author:
    William C. Shiel Jr., MD, FACP, FACR

    Dr. Shiel received a Bachelor of Science degree with honors from the University of Notre Dame. There he was involved in research in radiation biology and received the Huisking Scholarship. After graduating from St. Louis University School of Medicine, he completed his Internal Medicine residency and Rheumatology fellowship at the University of California, Irvine. He is board-certified in Internal Medicine and Rheumatology.

Hair, lanugal: The downy hair on the body of the fetus and newborn baby.

The lanugal hair (or lanugo) is the first hair to be produced by the fetal hair follicles. It is very fine, soft and usually is unpigmented.

The lanugal hair is prenatal hair. It appears at about 5 months of gestation and begins to be shed at 7 and 8 months of gestation.

The postnatal hair that succeeds the lanugal hair is conventionally divided into vellus and terminal hair. The vellus resembles the lanugal hair in that it is short, soft and usually unpigmented. The terminal hair is longer, coarser and usually pigmented. There are intermediate types of hair. Any given follicle can change the type of hair it is making.

"Lanugo" is the Latin word for down, like the fine small hairs of plants.

Reviewed on 9/7/2018

Health Solutions From Our Sponsors