Hair Cycle and Hair Loss

hair phases
At Modena Hair Institute we care scrupulously about the details and processes behind hair cycle and loss. Knowledge of hair cycles (or phases) are foundational to understanding the nature of hair loss, as hair thinning and problems with hair growth occur when your growth cycle is disrupted. This can be triggered by conditions such as metabolic disturbances, illness or improper nutrition.

The hair cycle is the all-important mechanism regulating hair growth in the body. Normally, each individual hair strand follows its own hair cycling schedule, completely independent of other hairs on the scalp.

In the following article we will dive into the nature and consequences of hair growth cycles.

The average adult human scalp begins with approximately 100,000 individual hair follicles, and each one of these follicles is constantly undergoing a regular cycle of growth, shedding, and re-growth. This means that the average, healthy person naturally sheds between 50 and 100 hairs from the head every day.

However, this loss goes largely unnoticed since, unlike other mammals, human hair growth and shedding is random, not seasonal, so the follicles are almost never in the same phase simultaneously. More likely, at any given time a random number of hairs will be in one of three distinct stages of hair growth and shedding: the anagen, the catagen, and the telogen phases.

Anagen Phase: Aggressive Growth
During this phase, the cells in the root of the hair are dividing rapidly, and the hair is growing about half an inch per month, or six inches per year. This new hair pushes through the dermis to the surface of the scalp, dislodging older hair along the way. Scalp hair can remain in an active growth phase for anywhere from two to six years, depending on an individual’s genetics, which is why some people find it easier to grow their hair longer than others. At any given time, about 75% of the hairs are in the anagen phase.

Catagen Phase: A Brief Transition
After the anagen phase comes the transitional catagen phase, a relatively short period, lasting about two to three weeks, when growth stops and the follicle effectively renews itself. During this phase the outer root sheath shrinks and attaches to the root of the hair, forming a stubby hair which is easily shed. This shrinking of the hair follicle is similar to what occurs during common genetic hair loss or androgenetic alopecia, but in the case of the catagen phase is only temporary.

Telogen Phase: Shedding
When the hair enters the telogen phase, it remains completely ‘at rest’ for roughly 100 days. During this time the follicle begins producing a new anagen hair shaft, which pushes out the fully formed club hair that is still resting on the surface. Pulling out a hair in this phase will reveal a solid, hard, dry, white material at the root. Only about ten percent of the hairs on the scalp are in the telogen phase at any one time, except in cases of telogen effluvium, a relatively uncommon form of hair loss that can be brought on by significant physiological stress.

Understanding the regular pattern of hair growth gives us important insights into the progression and underlying causes of hair loss, so it is something that the hair restoration experts at the Modena Hair Institute spend a great deal of time studying.

Dr. Amir Yazdan, MD, is an internationally renowned hair transplant surgeon, expert guest on Dr. Phil and The Doctors, creator of the GroMD hair restoration product line, ISHRS member, accredited member of the IAHRS and a visceral advocate for patient care. Learn more about Dr. Yazdan or read rave reviews from his patients.