curly hair

Hair growth cycle

Hair growth cycle is a biological process. Growing one strand of hair is a combination of known cellular mechanisms and a balance of macro and micro-nutrients. You are born with all of the potential hair strands that you will ever have. Hair follicles do not multiple as we grow. It is important to protect our hair to prevent unwanted hair loss or damage. The life cycle of hair can be categorized into three stages. The growth stage, transitional phase and a resting phase.


The hair that you can see with the naked eye is the hair shaft and is only one small part of an invisible network of sections including the hair follicle. Below the skin the hair strand extends deep into the skin into the hair root.  New hair cells are stored in the hair bulb. As they mature and harden, they attach to the bottom of the existing hair root. This pushes new hair up and out of the skin, resulting in the hair on your head getting longer. This happens at the average speed of one centimeter per month. In some people, hair growth can reach up to half inch per month. Despite shampoo and treatment promises you are unlikely to make the actual hair strand grow faster than a half-inch per month. However, there are important self-care steps that can be taken to decrease breakage which can interfere with maximum hair growth.

As long as new hair cells are growing and multiplying in the hair bulb, new hair can be grown. This is referred to as the growth phase, otherwise known as the anagen phase. Hair can grow differently in the growth phase depending on location. For hair on the head, the growth phase can last many years. For eyelashes and eyebrows, the growth phase may only be days.  If hair is cut in the growth phase, the strand will continue to grow and lengthen. If the hair shaft has fallen out and the hair bulb is empty, new cells can generate a new hair shaft. This allows the entire process to begin again.  

The transitional phase can also be called the catagen phase. During this time, the hair is not actively growing. The transitional phase lasts a few weeks and is the ending of the growth phase and moving into the resting phase.

The resting phase is the phase where the hair has stopped growing and falls out. This may last a few months. In this phase the hair strand permanently breaks away from the blood supply. It is important to note that only about 3-5% of all hair strands are usually ever in the resting phase. In case of extreme illness, stress, hormonal changes, vitamin deficiencies or other physical stress this might increase the percentage of strands in the resting phase beyond 5-10%. This is a survival strategy to conserve energy and resources for other parts of the body. Once those stressors are passed it is common to regrow new hair strands. The resting phase is a normal development in the life cycle of a hair strand.




When hair is moving through the three cycles, hair loss can be minimal and barely noticeable. Almost 90% of all hair strands are in the growth phase under normal circumstances. If many hair strands enter the resting phase at the same time, noticeable hair loss may be seen. The American Academy estimates we lose between 50-100 hair strands each day. This is normal and is not a concern for unusual amounts of hair loss. If you believe your hair loss is more than that, you may consider seeing a medical professional to investigate other factors.

As we age our hair that is produced in the hair follicle can become thinner, more brittle or change color. Oil glands can shrink with age resulting in hair than can break easier or appear dry. Some age-related changes may make it appear as if you are experiencing hair loss, when it may be a natural cellular response. Keeping your hair healthy while moving through the different hair phases can minimize the effects of daily hair loss and maximize hair growth.

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