Eyebrows are a defining feature of the face, serving both a communicative function through facial expressions and a protective one by diverting sweat and debris from the eyes. Many people wonder about the speed of their growth, especially after an over-plucking incident or noticing natural thinning. Eyebrow hair follows a unique biological cycle that makes its growth distinctively slower and shorter than the hair on your scalp. Understanding the science behind this process helps manage expectations for regrowth.
The Measured Speed of Eyebrow Growth
Eyebrow hairs grow at a measurable, yet comparatively slow, pace. On average, a single eyebrow hair grows about 0.14 to 0.16 millimeters per day. This rate translates to approximately 1 to 2 centimeters of growth over an entire year, which is significantly slower than other body hair. Scalp hair typically grows at a rate of about 0.3 to 0.4 millimeters per day. This slower speed is the primary reason why eyebrows do not grow into long strands. If an eyebrow is removed, complete regrowth to its full length typically takes anywhere from four to six months.
The Three Phases of the Hair Growth Cycle
The length and growth speed of any hair are determined by the hair growth cycle, which consists of three main phases: anagen, catagen, and telogen. The anagen phase is the active growth period where the hair follicle rapidly divides cells to lengthen the hair shaft. For scalp hair, this phase can last for years, allowing for long growth.
The difference in length is due to the extremely short anagen phase for eyebrows, which typically lasts only about 30 to 45 days. This short window dictates the maximum length an eyebrow hair can reach before it moves to the next stage. The catagen phase, or transitional stage, lasts for only a few weeks as the hair growth stops and the follicle shrinks.
Following the transition is the telogen phase, the resting period, which is the longest stage for eyebrows, lasting between two to four months. During this time, the fully grown hair remains in the follicle before eventually shedding to make room for a new hair. Because the growth phase is so brief, any disruption, like tweezing, forces the follicle back to the beginning of this lengthy cycle, delaying regrowth.
Why Growth Speed Varies
The rate at which eyebrows complete their cycle can vary significantly between individuals due to a combination of internal and external factors. Genetics plays the most substantial role, predetermining an individual’s natural hair thickness, density, and the programmed duration of their anagen phase. Age is another significant factor, as the hair growth cycle naturally slows down over time, leading to thinner, sparser eyebrows that do not regrow as quickly as they did in youth.
Proper nutrition provides the necessary building blocks for growth, as hair is primarily made of the protein keratin. Deficiencies in specific nutrients, such as iron, biotin, and certain vitamins, can hinder the hair follicle’s ability to sustain a healthy growth phase. Underlying health issues, including thyroid disorders or hormonal fluctuations, can also disrupt the delicate balance of the growth cycle, prematurely pushing hairs into the telogen phase and resulting in noticeable thinning.