The belief that cutting hair causes it to grow faster is a persistent idea passed down across generations. Many assume that removing the ends of a hair strand somehow signals the body to accelerate new hair production. Understanding the biology of hair growth allows for a clear distinction between the visible, dead portion of the hair and the living structure responsible for its creation.
The Science of Hair Growth Rate
The speed of hair growth is fixed and determined internally, not by trimming the ends. Hair growth originates exclusively deep beneath the skin’s surface within the hair follicle, a living organ. The rate of growth is controlled by the dermal papilla, which is supplied by blood vessels providing necessary nutrients for cell division. The hair shaft, which is cut, is composed of dead keratin protein and has no biological connection to this living growth matrix. Cutting the dead tip has zero physical impact on the cell division rate occurring in the follicle.
The Three Stages of Hair Life
The maximum length of hair is predetermined by a cyclical process known as the hair growth cycle, which is divided into three main phases: Anagen, Catagen, and Telogen. The Anagen phase is the active growth period.
During the Anagen phase, cells in the hair bulb rapidly divide, forming the hair shaft and pushing it outward. This phase can last anywhere from two to seven years, and its duration is the genetic factor that determines how long hair can potentially grow. Approximately 85 to 90 percent of scalp hair is in this active growing phase at any given time.
Following Anagen, the hair enters the Catagen phase, a brief transitional stage lasting about two to three weeks. Here, the hair follicle shrinks, and growth slows as the lower part detaches from the dermal papilla. The final stage is the Telogen phase, a resting period lasting three to four months. During Telogen, the hair remains in the follicle but ceases all growth before being shed to make way for a new Anagen hair.
The Illusion of Faster Growth
The belief that trimming hair accelerates growth stems from the visual effects of a fresh haircut. People perceive faster growth because regular trims prevent the hair from breaking off at the ends. When ends become damaged, they split and fray, causing the hair to fracture higher up the shaft and stop increasing in length. By removing these damaged ends, a trim ensures the hair retains its newly grown length, making the growth appear faster.
A freshly cut end also creates a blunt, uniform edge, which contrasts sharply with the naturally tapered tips of older hair. This blunt cut creates an optical illusion, making the hair look and feel thicker and denser at the ends.