The growth and loss of hair may seem like a simple process, but the hair growth cycle actually involves four distinct phases: anagen, catagen, telogen, and exogen. These stages have been studied in great depth to better understand how hair grows and what might be done to prevent or treat premature hair loss.
Not every hair is growing at the same moment. In fact, only about 85% of hair follicles are producing new hair at any given time. The rest are resting. This cycle of growth and rest is known as the hair growth cycle. Understanding each stage can help solve common hair dilemmas and really support healthier hair.
The hair growth cycle is made up of four stages: anagen, catagen, telogen, and exogen. Each stage is crucial for maintaining hair density and overall scalp health. Disruptions to the cycle can lead to increased hair shedding, hair thinning, slower growth, or reduced hair density.
Hair grows in four distinct stages. The first three phases - anagen, catagen, and telogen - cover the growth and maturation of hair and the activity of the hair follicles that produce individual hairs. During the final, or exogen, phase, “old” hair sheds, though usually, a new hair is getting ready to take its place. Each phase has its own timeline, which can be affected by age, nutrition, and overall health.
The anagen phase is the longest and most active stage of the hair growth cycle. It is also called the ‘active phase,’ this is when your hair is growing most rapidly. Cells at the root divide quickly to form new hair strands. Hair grows at a rate of 1-2 cms per month, or around half an inch per month (roughly six inches a year), often faster in summer.
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During the anagen phase, your hair follicles are pushing out hairs that will continue to grow until they’re cut or until they reach the end of their life span and fall out. At any time, about 85% to 90% of the hairs on your head are in the anagen phase.
The anagen phase differs with different types of hair. For example, the anagen phase for eyebrow hairs and pubic hairs is much shorter than the phase for your scalp hairs. The length of the anagen phase is determined by genetics. The longer the hair stays in the anagen phase, the longer it will grow. Typically, it lasts for 3-5 years, but can be longer in some individuals with up to seven years in those of Asian descent, allowing hair to grow as long as three feet. The anagen phase naturally shortens with age, which can make hair growth slower and limit maximum length over time.
During this phase, cells neighboring the papilla in a germinative layer divide to produce new hair fibers, and the follicle buries itself into the dermal layer of the skin to nourish the strand. Mitotic activity in the hair bulb and dermal papilla resumes and forms the new hair shaft, pushing out the old inactive hair, or club hair, as the new hair advances. The matrix cells, which form the new hair, multiply rapidly and ascend into the follicular canal, dehydrate, and form the growing shaft. Hairs that are in the anagen phase during removal are more sensitive to the various treatment modalities than hairs in the telogen phase. Alteration of matrix cell activity during anagen, by whatever method chosen, increases the amount of time from removal to regrowth.
To maintain healthy hair during the anagen stage, it is important to eat a balanced diet and get enough sleep.
The catagen phase starts when the anagen phase ends and tends to last about 2 weeks, approximately 10 days. It is a transitional stage between the anagen and the telogen phase. This short phase signals the end of active hair growth. Individual hairs are cut off from their blood supply and cells that produce new hair.
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During this chapter, hair follicles shrink, and hair growth slows. The hair also separates from the bottom of the hair follicle yet remains in place during its final days of growing. During this phase, hair growth slows down by 50% and may stop altogether. Only about 3% of hair is in catagen at any given time.
The catagen phase allows the follicle to renew itself (in a sense). During this time, the hair follicle shrinks due to disintegration and the papilla detaches and "rests," cutting the hair strand off from its nourishing blood supply.
The telogen phase typically lasts around 2 to 3 months, approximately 100 days or three months. It is the shortest and least active stage of the hair growth cycle. About 9% to 15% of your scalp hairs are in this phase at any one time.
During this resting period, hairs remain in the follicle but are not actively growing. Hairs don’t grow during the telogen phase, but they don’t usually fall out, either. The telogen phase is also when new hairs start to form in follicles that have just released hairs during the catagen phase. Hairs stay anchored but do not lengthen, allowing the scalp to prepare for new growth.
The telogen (resting) phase of the hair follicle lasts about three months. The final product of a hair follicle in the telogen stage is a dead, fully keratinized hair (a "club hair").
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The exogen phase is essentially an extension of the telogen stage of hair growth. Some health experts include the shedding phase in the telogen phase, but many scientists have separated this stage into another part known as the exogen phase. The exogen phase is when individual hairs are released from the follicle and naturally fall out.
During the exogen phase, hair is shed from the scalp, often helped along by washing and brushing. Losing 50 to 100 hairs per day during the exogen phase is normal. The exogen phase can last several months, typically 2 to 5 months. Once shedding occurs, the follicle is ready to start the cycle again with a new anagen phase. During the exogen phase, new hairs are growing in the follicles as old hairs fall away.
Several factors can influence the duration of each phase of the hair growth cycle, including genetics, age, hormones, stress, and seasonal changes. Hair often grows faster in summer than in winter. Nutrition and overall health also play a key role.
As we get older, several natural changes can affect the hair cycle:
Understanding these changes can help you adjust your haircare routine and expectations, as well as explore treatments to maintain fuller, stronger hair.
Normally, each hair follicle works independently, which is why we all shed around 80-100 hairs a day instead of losing all of our hair at once. Disruptions to the cycle can however lead to increased hair shedding, hair thinning and slower growth or reduced hair density. Common triggers include:
For example, telogen effluvium can occur about 12 weeks after a major stressor or illness, causing many hairs to enter the telogen phase at once. This results in noticeable hair shedding during the exogen phase. If your cycle is consistently interrupted, hair may never stay in the anagen phase long enough to reach its potential length.
Every hair in your scalp normally goes through this hair growth cycle. However, certain genetic conditions - as well as other processes - can affect how the cycle progresses.
Male pattern baldness (MPB) is a genetic condition that affects most men as they get older. It’s a form of hair loss that causes areas of our scalps to stop producing hair. Changes to our hair growth cycle are to blame due to a hormone known as DHT.
DHT or dihydrotestosterone is a male hormone produced naturally by the body. Yet, when it accumulates over time, it’s known to weaken and damage your hair follicles. That process is known as miniaturisation, and, as a result, your follicles stop producing new healthy hair.
The hormone has a particular impact on your hair growth cycle. DHT has been found to shorten the anagen phase (the growth phase) and lengthen the telogen phase (the resting phase). More accurately, DHT causes the catagen stage (the transitional phase) to occur much sooner. That means your hair doesn’t grow for as long while it rests for much longer. As a result, you’ll see more hair shedding, much slower growth, and often areas of baldness spreading across the scalp.
If you experience sudden hair loss across your scalp, you may be experiencing telogen effluvium. This is when your hair follicles quickly move from the anagen to the telogen phase due to trauma or stress. The result is that lots of hairs are shed at the same time.
Alopecia is a hair loss disease that can occur in anyone at any stage of life. Specifically alopecia areata is an autoimmune disease that causes hair to spontaneously fall out. It is mainly characterized by bald patches on the scalp or other parts of the body, and can ultimately cause baldness across the entire body. This disease interferes with the hair growth cycle by causing a follicle to prematurely leave the anagen, or active growth, phase and enter the resting, or telogen, phase.
Traction alopecia is caused by adding too much strain on the hair on one's head. Tight ponytails and other styles that require added tension to the hair are often what cause this disease. It can also occur on the face in areas where the hair is often styled. On the scalp, the hair is usually known to be lost around the hair line, leaving the densest amount of hair at the crown.
Having healthy, fuller hair depends on genetics and hormone levels, which are largely beyond your control, as well as manageable factors related to a healthy lifestyle and proper hair care.
Because hair is largely made of protein, you should keep up your protein intake by focusing on healthy proteins. That includes lean meats, fish, beans, legumes, and low-fat dairy products.
A 2018 study in the journal Dermatology and Therapy also found that getting enough of the following nutrients was associated with healthy hair growth:
Some good nutritional supplements to help maintain hair health are ones that contain biotin, iron (especially for women), vitamin C, vitamin D, vitamin B12 folic acid, zinc and omega-3 fatty acids. This is in conjunction to increasing your protein intake as hair is mostly made from protein. Supplements containing amino acids, protein, biotin, zinc and other nutrients can support follicle function and keep hair in the growth (anagen) phase longer. Products like Density Amino Acid Protein Booster and Healthy Hair Complex are great for giving additional support.
Hair growth relies on a consistent intake of protein, carbohydrates and healthy fats. Nutritional supplements like Density Amino Acid Protein Booster and Healthy Hair Complex can provide extra support to help keep your hair in optimal condition.
Physical and mental stress may contribute to premature hair loss due to several conditions, including the following:
Handling stress is key. If you’re experiencing stress, your hair may spend more time in the resting phase of the growth cycle. This means that new hair won’t be growing as quickly. Try the following preventive strategies, which have numerous health benefits:
Stress can trigger extra hair shedding, so trying strategies to reduce and manage stress can help protect your hair.
Healthy hair care starts with choosing the right shampoo. Look for products designed for your type of hair, whether it’s oily, dry, fine, or color-treated. The conditioner you use can also make a difference, but finding the right products may take some trial and error. Pay attention to how your hair responds to various shampoos and conditioners.
To have healthy hair, you need to be mindful of the products you use and how you treat your hair. Start by finding shampoos and conditioners that are designed for your hair type, whether it’s oily, dry, fine, colour-treated, etc. You may need to try a few different products before you find ones that work well for you. Be gentle with your hair to avoid damaging it. Use lukewarm water when shampooing and towel-dry your hair gently. Hair is more vulnerable to damage when it’s wet. Turning down the heat when drying your hair may also make a difference.
Treating your hair gently is also important for promoting healthy growth. Avoid very hot water when you shampoo, and towel dry your hair gently when you’re done. Hair is more vulnerable to damage when it’s wet. Turning down the heat when drying your hair may also make a difference.
Using products tailored to your hair type and concerns (whether thinning, limpness or dryness) really helps your hair make the most of whichever stage of the cycle it is in. A healthy scalp is the foundation for healthy hair growth. Regular cleansing, gentle exfoliation, and targeted scalp treatments can remove buildup, promote circulation and support follicles in maintaining an optimal growth cycle.
If you’re experiencing male pattern hair loss, you don’t need to just sit back and watch it happen. There are ways you can intervene in the hair growth cycle to encourage hair regrowth. Look for methods that lengthen the anagen phase of the cycle while shortening the telogen phase. Two solutions have been proven to be effective at doing just that:
Minoxidil is effective in about two-thirds of men - Finasteride in over 80%. When used as combined therapy, they have an efficacy of nearly 95%.
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