Every strand of hair on your head is going through its own quiet process, completely independent of the ones next to it. At any given moment, different hairs are growing, resting, or shedding -and that’s entirely normal. Understanding why this happens, and what each phase actually involves, can change the way you look at hair loss and hair health altogether.
The Hair Follicle: Where It All Begins
Before getting into the phases, it helps to understand what a hair follicle actually does. Each follicle is a small, living structure embedded in the scalp. It isn’t just a tube that hair grows out of -it’s metabolically active tissue that cycles through periods of growth, transition, and rest on its own internal clock.
This cycle repeats throughout a person’s lifetime, though the quality and duration of each phase can be influenced by age, nutrition, hormones, stress, and genetics. When the cycle gets disrupted, hair loss or thinning often follows.
The Anagen Phase: Active Growth
This is the phase most people care about, and for good reason. The anagen phase is when the hair is actively growing, with cells at the base of the follicle dividing rapidly to push the strand upward. This phase can last anywhere from two to seven years, depending on genetics and overall health.
The longer a hair stays in anagen, the longer it will grow. People who struggle to grow hair past a certain length often have a shorter anagen phase -their follicles simply transition out of growth mode earlier than others. Around 85 to 90 percent of all scalp hairs are in this phase at any given time.
The Catagen Phase: A Brief Transition
Once the anagen phase ends, the follicle enters catagen -a short transitional phase lasting roughly two to three weeks. During this time, the hair stops receiving nutrients from the blood supply, and the lower part of the follicle shrinks and detaches from its base.
The hair strand itself isn’t shed yet, but it’s no longer growing. Think of it as the follicle taking a breath before it moves into rest mode. Only about one to two percent of hairs are in catagen at any point, which is why it’s rarely discussed, even though it plays a critical role in the cycle.
The Telogen Phase: Rest and Release
The telogen phase is when the follicle goes quiet. The hair sits in place without growing, and this resting period can last around three to four months. At the end of telogen, the hair is naturally shed -often during washing or brushing -and a new anagen cycle begins beneath it.
Roughly 10 to 15 percent of hairs are in telogen at any time. When something disrupts the body -severe stress, illness, sudden weight loss, hormonal changes -a much larger percentage of follicles can enter telogen simultaneously. This leads to a condition called telogen effluvium, where noticeable shedding occurs two to three months after the triggering event.
The Exogen Phase: Active Shedding
Some researchers distinguish a fourth phase called exogen, which refers specifically to the shedding of the old hair strand. While this overlaps with telogen, it’s considered a separate biological event -the point at which the scalp actively releases the club hair (the detached strand) to make way for new growth.
Losing 50 to 100 hairs a day is considered normal during exogen. When the number climbs significantly beyond this range consistently, it’s worth looking at what might be interfering with the cycle.
What Disrupts the Hair Cycle
The stages of hair growth are sensitive to systemic changes in the body. Some of the more common disruptors include:
- Nutritional deficiencies, particularly iron, zinc, and biotin
- Thyroid imbalances that slow or accelerate follicle activity
- High levels of DHT (dihydrotestosterone) in androgenetic alopecia
- Chronic stress, which elevates cortisol and shortens the anagen phase
- Scalp conditions that affect follicle health at the root level
Brands like Traya approach hair loss by identifying which of these internal factors are at play before recommending any treatment -recognizing that restoring the cycle means addressing the cause, not just the symptom.
Final Thoughts
Hair loss rarely makes sense until you understand what the hair cycle is actually doing. When a phase gets cut short or thrown off rhythm, shedding increases and growth slows -not because the follicles are damaged beyond repair, but because something in the body is sending the wrong signals. Getting to the root of that disruption, quite literally, is where any meaningful recovery begins.
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