Babies are born with eyelashes, though their appearance can vary greatly at birth. Eyelashes are specialized, short hairs that grow along the edge of the eyelids. They develop long before a baby makes their appearance and are one of the earliest forms of hair to develop, serving a function beyond mere aesthetics.
Fetal Development of Eyelashes
The formation of the hair follicles that produce eyelashes begins early in gestation. Initial hair growth often starts around the 13th to 16th week of pregnancy. Eyelashes, along with eyebrows, become visibly established around the 20th to 22nd week of development, placing their formation firmly within the second trimester.
By the 26th week of gestation, the eyelashes are well-formed and clearly visible on the developing fetus. All the hair follicles a person will ever possess are fully formed before birth. This development occurs alongside the growth of lanugo, the fine, downy hair that temporarily covers the fetal body.
Eyelashes are distinct from lanugo, which usually sheds before or shortly after birth. The length and density of these prenatal lashes are primarily determined by genetics. The follicles are fixed in place and ready to produce hair before the baby is born.
The Biological Role of Eyelashes
Eyelashes serve as a physical barrier for the eyes. They act like a tiny net, catching small airborne particles such as dust, debris, and insects before they reach the delicate surface of the eye. This filtration helps maintain the health of the ocular surface and prevents potential injury.
Eyelashes are also highly sensitive sensory organs. The slightest touch triggers an involuntary and rapid blink reflex. This reflex is an immediate, protective action that quickly closes the eyelid to shield the eye from perceived threats.
Aerodynamic studies show that the optimal length for an eyelash is approximately one-third the width of the eye opening. This ratio helps deflect airflow away from the eye, minimizing tear evaporation and reducing the deposition of fine particles. This natural design helps keep the eye moist and clean, a process that is fully functional even in a newborn.
Eyelash Growth and Appearance in Newborns
While all newborns possess eyelashes, they may not always be immediately noticeable. In some babies, the lashes can be very fine, short, or light in color, especially in infants with blonde or pale hair, making them appear almost invisible. Premature babies may have shorter or less developed lashes because they missed the final weeks of in-utero growth.
Eyelashes grow in a cycle that includes an active growth phase, a transition phase, and a resting phase. This cycle is much shorter than the cycle for scalp hair. Lashes are constantly being shed and replaced, though the process is slow and often goes unnoticed.
The density and length of the lashes often increase over the first few months of life. Parents can expect a significant change in visibility within the first six months. As the baby matures, the hair often thickens and may darken, causing the lashes to become more prominent.