Hair Growth Stages: What To Know

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Medically reviewed by Susan Bard, MDMedically reviewed by Susan Bard, MD

Hair growth is a continuous process. There are four stages of hair growth: anagen, catagen, telogen, and exogen. Each stage of the process lasts for a different amount of time, ranging from a couple of weeks to eight years for one strand of hair.

In the hair growth cycle, your hair goes through a cycle of shedding and new growth that is influenced by multiple factors like genetics and your haircare routine.

As cells multiply, they harden and stick together to create a full strand of hair extending from the hair follicle (a tube-shaped opening on the skin's surface where hair grows).

Anagen Stage

Anagen is the most familiar stage of hair growth. In the anagen stage, hair follicles (a combination of skin and hair tissue) produce a hair shaft—the visible part of the hair that emerges from your skin.

As the most active hair growth phase, the anagen stage can last anywhere from 2-8 years for a strand of hair.

About 85-90% of the hair follicles you can visibly see are in the anagen growth stage. The length of the anagen phase decreases as we age, which results in hair that becomes thinner and more fragile over time.

During the anagen growth phase, hair grows straight, curly, or coily from your roots, depending on the shape of the hair follicle. For instance, round-shaped hair follicles grow straight. However, the more oval-shaped the hair follicles, the curlier the hair will be.

Catagen Stage

The catagen stage is the transitional phase that moves the hair from the anagen to the telogen stage. It lasts for about 2-4 weeks.

The catagen stage is one of the two rest stages of hair growth. In this stage, the hair follicles detach from the papilla (a structure that supplies blood to the roots of your hair).

This detachment results in cell death at the root of the hair follicle. Your hair loses about one-sixth of its standard diameter in this phase. A club hair (a hair strand that has stopped growing) is formed as a result.

Telogen Stage

The telogen stage is the resting phase of a strand of hair that lasts about 2-3 months. About 9% of the hair on your head is in the telogen phase at any time. During this phase, the hair follicle is at rest, and hair growth does not occur.

Exogen Stage

The exogen stage is the hair-shedding phase of growth. The exogen stage marks the end of the telogen phase and the beginning of the anagen stage. During this phase, new hair continues to grow upward, which pushes dead hair out while shedding old hair.

Factors That Affect Hair Growth

Many factors affect hair growth. Certain health conditions may prevent hair growth. Natural processes like aging and lifestyle factors that affect emotional and mental health can also influence hair growth.

Nutrients

Getting enough vitamins and minerals in your diet can promote faster hair growth. However, being deficient in certain nutrients can stunt hair growth throughout its stages. For example:

• Iron, selenium, and zinc supplements have been associated with hair cycle regulation. However, more research is needed to determine how much these nutrients affect hair growth.
• Low protein intake or iron deficiency can lead to acute telogen effluvium (TE). TE is a temporary form of hair loss, causing rapid hair shedding over a short period of time.

Studies have also found an association between nutritional deficiencies and chronic (long-lasting) TE, androgenetic alopecia (AGA), and alopecia areata (AA).

Alopecia is partial or complete hair loss. It is a chronic autoimmune condition resulting in patches of hair loss. Androgenic alopecia is a common form of alopecia triggered by androgen hormones. You are more likely to have androgenic alopecia, also known as male pattern baldness, if there is a history of it in your family.

Age

Age can affect the color and thickness of your hair. As you get older, you may also see changes in the texture of your hair as hair follicles change.

Changes in hair due to aging affect your hair's look and manageability. For example, some people may experience curlier hair. Your hair may also gradually become thinner over time.

Pregnancy

During pregnancy, levels of estrogen and other naturally occurring hormones (such as progesterone and prolactin) increase. Higher estrogen levels have been associated with faster hair growth and less hair shedding during pregnancy. Some researchers believe other hormones like thyroid and estrogen increase during pregnancy, contributing to hair growth.

Menopause

Menopause most often starts between the ages of 45-55 for people assigned female at birth. Menopausal symptoms include hot flashes, sleep disturbances, and mood swings. During menopause, levels of estrogen and progesterone decline.

One study found that postmenopausal women have a higher risk of alopecia. Additionally, losing estrogen during menopause is associated with decreased hair density. The anagen phase may also be shorter during this period.

Medications

Medications for certain health conditions can also affect the hair growth phases. For example, cancer treatments such as chemotherapy can affect the cells in your body that are responsible for hair growth. Additionally, chemotherapy can accelerate the transition to the telogen stage, which can lead to hair loss.

Stress

Stress often makes it harder for hair strands to leave a state of rest where no hair growth occurs. Chronic or acute (short-term) stress has also been found to cause hair growth conditions such as TE. It may also increase the likelihood of developing alopecia.

Genetics

Many people with similar ancestry also have similar hair textures. The thickness of your hair, too, can also come from genetics. How fast your hair grows may depend heavily on your genetics just as much as your hair texture does.

According to research, Asian hair has been found to grow at a faster rate across nationalities. The structure of hair fibers and longer diameter contribute to accelerated growth.

It is typically harder to see the growth in Black hair textures with a tighter curl or coil where the hair grows in a different direction. Studies have found that the larger the diameter of the hair fiber, the faster the rate of hair growth.

How To Promote Hair Growth

Although, some hair growth practices to keep your strands healthy depend on the texture of your hair. Eating nutrient-dense foods is beneficial for all hair types. Consuming anti-inflammatory foods like nuts and berries has been found to activate hair out of resting growth phases.

Try to manage your stress for more hair growth and your overall health. Studies show that elevated levels of cortisol (your body's primary stress hormone) can affect how quickly your hair goes through the growth stages.

Add massaging your scalp to your haircare routine while washing or before styling. Massaging your scalp increases blood flow and stimulates the hair follicle. It promotes the telogen-to-anagen transition of hair growth.

Overall, you want to ensure a thorough haircare routine to encourage growth. Use conditioner after every shampoo, heat-protectant products during heat styling, and a weekly deep conditioning mask to minimize damage. For curly and coily textures, it's important to keep your hair as moisturized as possible at all times.

When To See a Healthcare Provider

See a healthcare provider or dermatologist (a doctor treating skin, hair, and nail conditions) if you are experiencing hair loss or hair thinning.

A dermatologist can help you find the cause of your hair loss. They first start by examining your scalp for any signs of a skin condition affecting growth. They will ask how long you have been experiencing hair loss to better understand what may be happening.

A healthcare provider may suggest a blood test or scalp biopsy (taking a sample of your scalp to evaluate in a lab) if they feel it is necessary. A blood test or scalp biopsy lets your healthcare provider know if an infection, hormonal imbalance, or nutritional deficiency is causing you to lose hair.

Your provider may prescribe medication or an over-the-counter (OTC) product to stimulate hair growth as part of your treatment plan. In the case of nutrient deficiency, they may also recommend a dietary supplement. OTC medications like Propecia (finasteride) and Rogaine (minoxidil) are commonly used to treat hair loss.

A Quick Review

The hair growth cycle has four stages—anagen, catagen, telogen, and exogen. Anagen is the growth phase, catagen is the transition phase, telogen is the rest phase, and exogen is the last phase of the cycle that involves shedding of the hair.

Stress, nutritional deficiencies, and certain infections can cause hair loss. See a dermatologist to better understand how to treat or prevent hair loss.

Read the original article on Health.com.