Human body is covered with approximately five million hair follicles all round the body except, of course, the lips, the sole of the feet, and the palm of the hands. All these hair follicles undergo three hair growth stages: the anagen or the growth stage, the catagen or the transition phase, and the telogen or the resting period. The amount of time the hair spends in these hair growth stages usually determines the length of growth of the hair. Drastically, the scalp hair grows much longer than other body hair.
The anagen phase is where about eighty to ninety percent of the hair is. An average growth of about 1 centimeter every 28 days happens because hair is active for growing in this stage. Scalp hair stays in this stage around 100 days or more, to as long as six to eight years, while other body hair would only stay for just four to seven months. This is why the scalp hair is more capable of growing longer than other body hair. Of all the hair growth stages, this is where the largest percentage of the hair is and obviously where the hair stays the longest.
Next to anagen is the catagen phase. Hair growth in this stage is no longer active. The death of hair cells explains mainly the reason for this, thus stopping hair growth. Scalp hair stays in this stage for one to three weeks, while other body hair could last up to four weeks. When this phase is about to end, production of new hair would take place.
The last phase is telogen. Around eight to ten percent of hair is in this stage. This figure represents the average of fifty to one hundred hair falls each day. A closer examination of the shed hair will reveal a white, dry, and usually hard thing in the root which signifies that the hair is not actually damaged; it just needs a natural shedding. Scalp hair is under this stage for about three months; other body hair would be here for almost nine months. Growth stage will come closely after this phase.