The human body consists of approximately 5 million hairs distributed all over the body except the palms, soles, lips, and genitalia. The scalp only contains about 100,000 hairs. Most people understand the aesthetic role of hair — however, hair also performs temperature regulation, protection, and sensory perception. Read on to learn about hair growth, what controls it, and if you can increase it.
Hair grows within hair follicles and emerges through pores in the skin.
There are four stages of hair growth — anagen, catagen, telogen, and exogen.
Several factors influence hair growth, such as genetics, medical problems, medications, gender, age, hair care practices, and nutrition.
Hair grows at a predetermined rate based on genetics. It averages about one-half an inch per month.
While you cannot increase hair's growth rate, some interventions will keep hair healthy.
How does hair grow?
Hair, which consists of the protein keratin, grows from hair follicles that lie deep in the skin and emerge through pores (openings in the skin). Skin cells (keratinocytes) synthesize keratin. As the skin cells make more keratin, hair increases in length. Sebaceous oil glands connect to the follicles and secrete oil on the hair as it exits through the pore. This oil lubricates and protects the hair.
The shape of the follicle determines the texture of the hair. Round follicles create straight hair, while oval follicles produce curly hair. The follicle shape is genetically determined and cannot be changed.
Stages of hair growth
Hair growth consists of four stages of varying time lengths. Every hair goes through these stages in order. However, the length of the stages will differ depending on the location of the hair on the body.
Here are the stages:
- Anagen. This is the growth stage of the hair, which can last 3-5 years. Most hairs on the scalp and body are in this stage at any given time. Body hairs have a shorter anagen stage of a few weeks, so they cannot grow long like scalp hairs.
- Catagen. This is the transition stage of hair growth which lasts several days. Growth slows down during this stage.
- Telogen. This is the resting stage that lasts several months.
- Exogen. Many consider this stage a part of telogen, while others believe it is a separate stage. This is the shedding stage which can last several months. It is normal to lose 100 hairs a day during this stage.
How fast does hair grow normally?
The rate at which healthy hair grows is mostly genetically determined. However, on average, hairs grow about one-half inch or one centimeter a month and approximately six inches or twelve centimeters a year. Coily hair tends to grow slower. Also, after 30, hair growth slows. Hairs on the scalp grow faster than hair on other body parts, such as eyelashes.
What influences hair growth?
In addition to genetics, other factors influence the growth of hair, such as:
- Medications. Medications, such as steroids or chemotherapy, can slow hair growth.
- Coexisting medical problems. Medical problems, like thyroid problems or hormone imbalances, slow hair growth.
- Nutrition. Poor nutrition affects the health of your hair.
- Age. Hair grows slower as you age.
- Gender. Women's hair tends to grow slower than men's.
How fast does hair grow back after:
Hair grows back at different rates depending on the insult that occurred. It also varies from person-to-person based on the factors mentioned earlier. These are some growth rates for common hair loss issues:
- Haircut or shaving. Despite the myth that hair grows back quicker after shaving or haircut, it does not. It grows about one-half inch a month. Also, hair does not grow back thicker after shaving.
- Chemotherapy. It can take several weeks after the chemotherapy ends before hair will begin to grow. It will take several months before soft fuzzy hairs regrow and emerge from the pores. Hair may grow back a different color or texture after chemotherapy. Some chemotherapies cause permanent hair loss.
- Androgenic alopecia. Androgenic alopecia, also known as patterned hair loss, is hereditary. It appears slowly over many years. Unfortunately, this type of hair loss is permanent. The good news is, if you catch it early, you can slow it down.
- Alopecia areata. This type of hair loss is autoimmune, meaning that your body attacks its hair follicles and causes hair loss. The course is rather unpredictable and may lead to permanent hair loss in some cases. This hair loss affects the scalp, face, and body. Early treatment can lead to faster regrowth.
- Telogen effluvium. Telogen effluvium is a temporary loss of hair due to a stressor. These can include illness, hospitalization, surgery, or emotional stress from a divorce or death in the family. It begins 3-6 months after the stressor occurs and can take months for hair loss to cease. In most cases, the hair loss is fully reversible.
- Thyroid and other medical problems. Hair loss caused by certain medical conditions, like thyroid problems, is not permanent. After receiving successful treatment for the medical condition, the hair usually regrows completely. It can take several months to see regrowth.
- Skin problems, like psoriasis and seborrheic dermatitis. Skin issues affecting the scalp, such as psoriasis and seborrheic dermatitis, can lead to hair loss. The hair loss is usually temporary. Once successful treatment has begun, the hair will regrow.
How to make hair grow faster
While you cannot increase the rate at which hair grows, you can help it regrow. The goal is to keep your hair healthy with proper care of your hair and body. Healthy hair grows the fastest.
Here are some tips for regrowing hair:
- Eat a well-balanced diet. This consists of proteins, carbs, and good fats. Also, vitamins and minerals are essential. There are some nutraceuticals designed to help hair grow.
- Proper hair care. To keep your hair healthy, you should avoid heat tools, chemical treatments, dyes, over washing, brushing wet hair, and tight hairstyles. Scalp massages may increase blood flow to deliver more nutrients and oxygen to the scalp, which may help hair grow.
- Medical interventions. Several medications can help with hair loss, such as topical minoxidil for men or women or oral finasteride for men. Medical treatments, such as PRP/PRF with or without micro needling or light therapy, can help regrow hair.
- Sun protection. Sun can damage the scalp and hair, so wear sunscreen on exposed scalp skin and a wide-brimmed hat outside. Hair sunscreens are also available.
- Lower stress levels. Stress can cause hair loss. Try exercise, relaxation techniques, or outings with friends to lower stress levels.
- Treat medical issues. If you have medical problems contributing to hair loss, talk to your doctor about beginning proper treatment.
- Check medications. Discuss with your doctor any medications which may be causing hair loss. See if there are alternative medications you can take.
Hair grows at a genetically predetermined rate. There is no way to increase the rate, but there are ways to ensure it is healthy and growing at its optimum. If you notice issues with your scalp or excessive hair loss, see your dermatologist immediately for treatment.
If I cut my hair will it grow faster?
No, hair does not regrow faster after a haircut. It will look better because the split ends are gone. Your hair will appear fuller and silkier when the damaged parts of the hair are no longer present.
- J Invest Dermatol. A guide to studying human hair follicle cycling in vivo.
- Indian J Plast Surg. Hair Cosmetics for the Hair Loss Patient.
- J Cosmet Dermatol. Treatment options for androgenetic alopecia: Efficacy, side effects, compliance, financial considerations, and ethics.