According to Dr. William Rassman, Medical Director and Founder of the New Hair Institute in Los Angeles, California, each hair on the scalp grows in a three-phase cycle.
Three Phases of the Hair Growth Cycle
- Growth phase (Anagen). This first phase of hair growth can last from two to six years. During this phase, hairs actively grow at about one-half inch per month. About eighty-five percent of hairs actively grow at any given time.
- Transitional phase (Catagen). This second phase of hair growth lasts about two weeks. During this phase, hair follicles shrink.
- Resting phase (Telogen). This final phase of hair growth lasts one to six months. Hair does not grow during this phase and some hairs shed. Ten to fifteen percent of hairs rest at any given time.
Dr. Rassman added that cutting hair or letting it grow does not impact the rate of hair growth.
According to Sarah Koessler, a consultant for The Hair Styler, the length of a person's anagen phase effects how much the hair grows. People who have a longer growth phase experience more hair growth in the same time period than those who have a shorter growth phase.
For example, a child with a short, two-year growth phase followed by transition and a long, six-month resting phase would result in relatively slow growing hair as compared to another child with a longer growth phase or shorter resting phase.
Changes to the Hair Growth Cycle
According to health and fitness reporter, Linda Tarr Kent, the average person has about 100,000 hairs, each made of proteins called keratin. Each day, a person sheds 50 to 100 hairs. A person does not form any new hair follicles after birth. However, hair size, color, and the growth cycle can change throughout a person's life.
For example, a child who begins life with a short hair growing phase can move into longer growing phases (or shorter resting phases) in subsequent years.
Medical Causes of Slow Growing Hair
When hair does not grow as expected, a dermatologist can assess the child for medical conditions that affect hair growth. Linda Tarr Kent listed the following factors which could impact the hair growth cycle.
- Medications
- Chemicals (See Home-Made Shampoo Recipes)
- Skin conditions
- Autoimmune disorders
- Diabetes
- Heredity
Loose anagen syndrome is one condition which can cause slow or non-growing hair. Hair in a person with loose anagen syndrome is often thin, sparse, and sometimes easy to painlessly pull out.
Foods to Support Hair Growth
Ripa Ajmera of Live Strong listed the following nutrients that support hair growth.
- Vitamin C helps the body create collagen, needed for hair and skin growth.
- Vitamin B helps create red blood cells, needed for distributing nutrients throughout the body.
- Zinc aids tissue growth and repair and supports oil glands around hair follicles.
- Iron helps transport oxygen to all of the body's cells.
- Protein helps the body create keratin.
A lack of B vitamins, namely B-6, folate, and B-12, causes hair follicle cells to grow slowly, shed quickly, or produce weak hairs. Zinc deficiency contributes to slow hair growth, hair loss, and dandruff (seborrheic dermatitis). A lack of protein results in slow-growing, weak hair.
Medical conditions that affect hair growth can also affect skin and nails. A child with slow-growing hair, but otherwise healthy skin and nails and a nutritious diet might simply have a relatively short hair growing phase. A dermatologist can assess the child for hair, skin, and nail conditions.
Sources:
Rassmun, William, MD. "My Daughter's Hair Won't Grow." BaldingBlog.com. July 14, 2006.
Kent, Linda Tarr. "Facts About the Speed of Hair Growth." LiveStrong.com. December 16, 2009.
Ajmera, Ripa. "Foods That Grow Hair." LiveStrong.com. December 17, 2009.
Sara McGrath - Sara is a veteran homeschool mom of three, Usborne consultant, and the author of Unschooling: A Lifestyle of Learning.
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