Have you ever wondered why the scalp hair grows to as long as the waist or even longer while other body hair does not grow this long? This can be explained by the differences in the length of time the scalp and other body hair stays in a certain hair growth phase.
Human hair undergoes three phases: the anagen phase also known as the growth phase, the catagen phase or the transition phase, and the telogen phase where hair is said to be at rest.
Anagen is the hair growth phase where the hair is actively growing. About eighty to ninety percent of a human’s total hair is at this phase. Averagely, hair grows about one centimeter every 28 days in this phase. Scalp hair is in this stage for two to three years, and sometimes could even last up to eight years while other body hair stay in this phase for to seven months. This explains primarily why scalp hair has more capacity to grow longer; just imagine that about half an inch a month that could continuously grow to up to eight years.
Next to anagen is the catagen phase, the hair growth phase where transition from the anagen to the end of active growth happens. The death of major hair cells causes the hair to stop growing actively. Scalp hair stays in this phase for two to three weeks while other body hair stays for three to four weeks. Again, this explains why scalp hair grows longer. Active growth stops longer for other body hair than that of scalp hair.
The last hair growth phase is the telogen or the resting phase. This is called the resting phase because this is when shedding happens, approximately fifty to one hundred hair fall per day. About eight to ten percent of hair is in this phase. The hair shed is usually not damaged but it must undergo a natural shedding as part of this phase. Scalp hair is in this stage for three months while other body hair for almost nine months. Not only does other body hair stays in the growth phase longer, it also “rest” longer.