Hair Growing to Hair Falling Out: The Life of a Follicle
Learn About Your Hair’s Natural Cycle
Hair falling out may trigger concerns of permanent hair thinning and loss, but a life of baldness is not necessarily in your future simply because you notice some strands on your pillow or in the shower drain. Each hair on your head and body has a natural lifespan that runs from growth to shedding.
When it comes to hair falling out, you should also know that it’s a daily occurrence. Healthy people can lose anywhere from 50 to 150 hairs each day as part of the natural cycle. These are hairs shed during the final of four phases in preparation of new hair emerging. Not all of our follicles are in the same phase at the same time, which is why we don’t see all of our hair falling out at once.
Anatomy of a Follicle
A follicle is essentially a cup in the skin, at the base of which sits a hair bulb. Cells that divide in this bulb, fed by attached blood vessels and controlled by hormones, form a hair shaft that grows up and out. As humans, we have about 100,000 follicles on our scalps, and about 5 million total follicles that cover our body from head to foot.
Each follicle is also connected to glands that produce oil and nerves that help us sense when our hair comes into contact with something that moves it. Some follicles are connected to muscles that raise the hairs when we’re cold or alarmed.
As noted above, each hair moves through four phases in its own follicle, and not all follicles are in the same phase at the same time.
The Four Phases of the Hair Growth Cycle
Anagen Phase
This is a hair’s growth phase. About 85 percent of a person’s hairs will be in this active phase at once. Hair falling out due to natural causes often signals the beginning of this phase, since new growth pushes old, inactive hairs up and out of the skin.
During anagen, a hair can grow approximately half an inch each month for two to eight years.
Catagen Phase
This is a hair’s degradation or transition phase. Over the course of a little less than two weeks, a follicle will shrink in preparation of the old hair’s ejection. The shaft disconnects from its blood supply, and the shrinking follicle pushes the hair upward, closer to falling out.
Telogen Phase
This is known as the resting phase. During this period of about three months, the hair sits as the follicle recharges itself and prepares to re-enter anagen.
Exogen Phase
This is when you finally see the hair falling out, though exogen hasn’t always been recognized as a distinct phase. Technically, it is the part of telogen when the shedding physically occurs, helped along by the emerging new growth that signals the start of a new cycle.
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Exceptions to the Rule
Sometimes, an external factor stresses out the body enough to suddenly shift follicles from the degradation or even growth phase into an immediate resting phase, prompting mass shedding. Hair falling out after a system shock can include up to 70 percent of the total hair on the scalp and even hairs on the body. This large amount of hair falling out is known as telogen effluvium, and it can be due to illnesses, fevers, and infections; physical or psychological stressors; labor and childbirth; thyroid or dietary imbalance; surgery; medications; and more.
Typically, patients who go through the sort of shock that can trigger telogen effluvium won’t notice hair falling out in greater numbers until weeks or months after the key event.
Since hair falling out due to telogen effluvium will slow over the next six to eight months, and new hairs will begin to emerge, treatments probably will not be necessary to restore a full head of hair. If the condition persists, however, or if there seems to be no likely reason there should be mass quantities of hair falling out, testing may be in order to determine whether there is an underlying medical condition that should be addressed.
