Quick definition: The catagen phase is the brief transition stage of the hair growth cycle, after active growth (anagen) ends and before the resting phase (telogen) begins. Over roughly two to three weeks, the hair follicle shrinks, the hair detaches from its blood supply, and a "club hair" forms that will later be shed.
What is the catagen phase?
Every hair on your scalp follows a repeating cycle. The main phases of hair growth are anagen (growth), catagen (transition), and telogen (rest and shedding). Catagen is the shortest of the three and the one people hear about least, but it is the step that lets a hair follicle reset and eventually grow a new hair.
At the end of anagen, the follicle receives signals to stop producing hair. According to the NCBI StatPearls chapter on hair physiology, catagen begins as anagen ends and is marked by a transition toward quiescence, or inactivity.
"the hair follicle undergoes apoptosis-driven regression" — StatPearls: Physiology, Hair
Apoptosis is programmed, orderly cell death. It is a normal, healthy process here, not a sign of damage.
What happens to the follicle during catagen?
Catagen is a controlled wind-down of the follicle's lower portion. The main events:
Growth stops. Matrix cells at the base of the follicle stop dividing, so the hair shaft stops lengthening.
Pigment production ends. The Wikipedia entry on human hair growth notes that melanin production in the hair bulb stops during this phase. That's why the root end of a shed hair is pale.
The follicle shrinks. Cells in the lower follicle are cleared away through apoptosis, and the follicle retracts toward the surface.
The papilla separates. The dermal papilla, the cluster of cells that supplies the growing hair, detaches, cutting the strand off from its blood supply.
A club hair forms. The base of the hair hardens into a rounded, fully keratinized "club" that stays anchored until it is shed in telogen or exogen.
"Ultimately, the follicle is 1/6 its original length" — Wikipedia: Human hair growth
The research behind catagen
Much of what we know about catagen comes from animal studies. A 1998 study in Archives of Dermatological Research by Matsuo, Mori, and Hashimoto used DNA fragmentation techniques in mouse follicles and confirmed that apoptosis occurs in the lower regions of the follicle toward the end of catagen. The study also noted that the precise mechanism behind catagen involution had not been fully resolved, which remains an active area of hair biology research.
How long does the catagen phase last?
Catagen is short. Wikipedia's hair follicle entry describes it as lasting about two to three weeks, while Cleveland Clinic puts it at about two weeks. Because it passes so quickly, only about 1–2% of scalp follicles are in catagen at any one time, compared with up to 85% in anagen.
|
Phase of hair growth |
What happens |
Typical scalp duration |
|
Anagen |
Follicle actively builds the hair shaft |
2–7 years |
|
Catagen |
Growth stops, follicle regresses, club hair forms |
About 2–3 weeks |
|
Telogen |
Follicle rests; old hair is shed |
About 3 months |
What can shift hairs into catagen early?
The timing of catagen is mostly set by each follicle's internal clock, but outside factors can end anagen sooner than normal. When that happens to many follicles at once, a wave of hairs passes through catagen and into telogen together, leading to noticeable shedding a few months later. Common triggers documented by dermatology sources include:
High fever, significant illness, or major surgery
Childbirth and other large hormonal shifts
Severe psychological stress
Crash dieting or low protein intake
Starting or stopping certain medications
This delayed-shedding pattern is called telogen effluvium. If you notice sudden, heavy shedding, see a board-certified dermatologist to identify the cause.
Common misconceptions
"Catagen means hair loss." It doesn't. Catagen is a normal part of every hair's life, and the follicle is preparing to start again.
"Hairs fall out during catagen." Usually not. The club hair typically stays in place through telogen and is released later.
"Catagen damages the follicle." The shrinking is programmed and reversible. The follicle's stem cell reservoir, located in the bulge area, stays intact for the next cycle.
Catagen in beauty and personal care
Catagen rarely gets named on product labels, but understanding it helps set realistic expectations for any hair or scalp routine.
Patience with results. Because each hair spends years in anagen and weeks in catagen, changes in how full hair looks take months to show, not days.
Reading your shed hairs. A shed hair with a small white bulb at the root is a normal club hair that has completed catagen, not a sign the follicle has been pulled out.
Scalp care. Keeping the scalp clean, comfortable, and free of heavy buildup supports the environment that follicles cycle in. See our guide to scalp coverage for how at-home scalp tools are designed.
Professional evaluation. When shedding changes suddenly, a dermatologist can examine hairs and the scalp to see how many follicles are in each phase.
How Reseen fits in
Reseen's scalp tools are built for steady, at-home scalp care rather than quick fixes, which matches how slowly the hair cycle moves. Weave is a handheld light comb with 39 × 660nm red VIPE™ precision light emitters, designed for a healthier-looking scalp and fuller-looking hair.
Halo, coming soon, is a wireless cap liner with 256 precision light points in red (660nm) and blue (460nm), with Daily Care, Scalp Balance, and Deep Care modes. Both are cosmetic devices meant to support scalp health as part of a consistent routine.
Frequently asked questions
What happens in the catagen phase?
Hair growth stops, pigment production ends, and the lower part of the follicle shrinks through programmed cell death. The dermal papilla detaches, and the hair becomes a club hair that will be shed in a later phase.
How long does the catagen phase last?
On the scalp, catagen usually lasts about two to three weeks. It is the shortest phase of hair growth, so only around 1–2% of scalp hairs are in catagen at any given time.
What are the phases of hair growth in order?
The order is anagen (growth), catagen (transition), and telogen (rest). Some sources add exogen, the shedding step, after telogen. The follicle then returns to anagen and begins a new hair.
Is catagen the same as hair loss?
No. Catagen is a normal part of every hair's cycle, and a healthy follicle will go on to grow a new hair. Persistent or unusual thinning is different and should be checked by a dermatologist.
Browse every term in the Reseen glossary.
Sources
Physiology, Hair — Hoover E, Alhajj M, Flores JL; StatPearls, NCBI Bookshelf, 2023
Human hair growth — Wikipedia, accessed 2026
Apoptosis in murine hair follicles during catagen regression — Matsuo K, Mori O, Hashimoto T; Archives of Dermatological Research, 1998
Hair follicle — Wikipedia, accessed 2026
Hair Follicle: Function, Structure & Associated Conditions — Cleveland Clinic, accessed 2026
This article is for general education and is not medical advice. Reseen devices are cosmetic devices and are not intended to diagnose, treat, cure, or prevent any disease. If you have a skin or scalp condition, talk to a board-certified dermatologist.