Eyelashes, scientifically known as cilia, are specialized hairs lining the edges of the eyelids. These short, curved hairs act as a sensory barrier, triggering a reflexive blink when touched by a foreign object to shield the eye. Eyelashes also protect the ocular surface from dust, debris, and moisture, helping the delicate tear film remain stable. Like all body hair, eyelashes are produced by hair follicles and undergo a continuous, cyclical process of growth, rest, and eventual shedding. This cycle determines the overall length and density of the lashes.
The Three Stages of Eyelash Growth
Each eyelash follows a three-phase growth cycle. The Anagen phase is the period of active growth where the hair follicle is connected to the blood supply. This phase is short for eyelashes, lasting approximately 30 to 45 days, which keeps them short compared to scalp hair. Eyelashes grow at a rate of about 0.12 to 0.14 millimeters per day during this period.
The Catagen phase is a brief transitional period lasting about two to three weeks. The hair follicle shrinks, detaching from the blood supply and halting growth. The eyelash reaches its full potential length but remains in place until shedding.
The final stage is the Telogen phase, the longest resting or shedding phase, lasting several months. The mature lash stays in the follicle while a new hair begins to form beneath it. The old lash eventually falls out naturally, restarting the cycle. Since each lash is on its own schedule, only a small percentage are shed at any time.
Eyelash Maturation and Stabilization
The question of when eyelashes “stop growing” is better understood as when their genetically predetermined growth cycle stabilizes. Eyelash follicles are programmed early, but the parameters of the growth cycle, specifically the duration of the Anagen phase, stabilize as a person matures. This stabilization typically occurs by late childhood or early adolescence. At this point, the maximum potential length and density, which are heavily influenced by genetics, become consistent.
The duration of the Anagen phase is the biological factor that determines the final length of the lash, and this duration is fixed after maturation. Unlike scalp hair, the eyelash growth cycle quickly establishes its fixed pattern. Once this cycle is set, it remains largely consistent throughout a person’s healthy adult life. Significant changes to the cycle’s predetermined length and density only occur much later in life due to aging.
Influences on Eyelash Length and Density
Although the growth cycle is genetically fixed after maturation, several factors can modify the appearance and health of mature lashes. Genetics remains the dominant influence, dictating inherent length and thickness. Hormonal fluctuations can also cause noticeable changes in density, such as thinning seen with thyroid issues or temporary growth increases observed during pregnancy.
Nutritional deficiencies, such as a lack of zinc, iron, or biotin, can compromise the hair follicle, leading to weaker or sparser lashes. External factors, including the chronic use of harsh cosmetics or improper makeup removal, can cause mechanical damage and premature shedding. Certain medications, most notably prostaglandin analogs used to treat glaucoma, can unintentionally extend the Anagen phase, leading to significantly longer lashes. Advanced age naturally causes the lash cycle to slow down, resulting in a gradual thinning of the eyelashes over time.