1. Anagen phase – The growth phase
The anagen phase is the longest and most active phase in the life cycle of a hair. On the scalp, it usually lasts between two and seven years. Its length varies from person to person and depends on genetic factors, age, hormone balance, and the affected area of the body. During this phase, the hair follicle is fully active: new cells are constantly being formed in the “hair matrix”:/en/haarmatrix.html , causing the hair to grow at an average rate of 0.3 to 0.5 millimeters per day. The hair root is deeply anchored in the scalp and is supplied with nutrients and oxygen via the dermal papilla. Approximately 85 to 90 percent of all hair on the head is in the anagen phase at any given time.
2. Catagen phase – The transition phase
After the anagen phase is complete, the hair enters the catagen phase, which is significantly shorter and lasts only about one to three weeks. In this phase, the hair root stops producing cells, active growth stops, and the follicle begins to regress. The connection to the blood supply is cut off, causing the hair follicle to shrink. The hair begins to detach from the nourishing papilla and keratinizes. Only about one to three percent of hairs are in the catagen phase at any given time. This phase serves as preparation for hair loss, which takes place in the next phase.
3. Telogen phase – The resting and shedding phase
The telogen phase is the resting phase in the hair cycle and lasts about two to four months. During this time, the hair rests completely in the follicle without continuing to grow. It is now completely keratinized and no longer actively connected to the hair follicle. Eventually, the hair is either loosened from the follicle by external influences such as combing, washing, or rubbing, or it is pushed out by the new hair growing back in the coming anagen phase. This process is completely natural and results in a daily hair loss of about 70 to 100 hairs. Around 10 to 15 percent of all hairs are constantly in the telogen phase.
The cycle begins again
After the end of the telogen phase, the cycle begins again: a new hair forms in the hair matrix, grows and pushes the old, loose hair out of the follicle. As long as the hair follicle is healthy, this cycle can be repeated many times – theoretically for a lifetime. The old hair that falls out is therefore not a sign of a disorder, but part of a natural renewal process.
Factors influencing the hair cycle
The hair growth cycle can be influenced or disrupted by many internal and external factors. Hormonal changes—especially those caused by the hormone dihydrotestosterone (DHT)—play a central role in this process. DHT can shorten the anagen phase and cause the hair follicles to shrink, which is often observed in androgenetic alopecia (hereditary hair loss).
Stress, psychological strain, illness, malnutrition, medication, or impaired blood circulation in the scalp can also influence the cycle. A common form of hair loss resulting from this is known as telogen effluvium: an above-average number of hairs are prematurely transferred to the telogen phase at the same time, which manifests itself in increased hair loss a few months later. Regional differences on the body also influence the cycle duration: while hair on the head can grow for years, the anagen phase of eyelashes, eyebrows, or leg hair lasts only a few weeks—which is why this hair never grows particularly long.
Conclusion
The hair growth cycle is a finely tuned biological process that determines the lifespan of each individual hair. As long as the hair follicle remains healthy, hair regrowth after natural loss is assured. Only when the follicle becomes permanently damaged or inactive—for example, due to genetic predisposition, hormones, or disease—can permanent hair loss occur. A basic understanding of this cycle is important not only for hair care and health, but also for aesthetic applications such as laser hair removal, where timing is crucial for success.
