Anything that disrupts the life cycle of hair
can cause hair loss, or alopecia
. Sometimes hair loss is temporary and reversible. If hair follicles are permanently damaged, however, the hair loss is permanent.
Types and Causes of Hair LossFemale-pattern baldness
, or female androgenic alopecia
(FAA), is not as well understood as male-pattern baldness. It may or may not be related to androgens, the hormones that cause male-pattern baldness.
If you have FAA, your hair will gradually thin out over several years in a specific pattern: hair loss will begin around the part and spread over the crown, or top, of your head. Hair loss can start at any age after puberty.
FAA affects about 10% of pre-menopausal women and 50–75% of women aged 65 and up. Alopecia areata (spot baldness)
is also hereditary and affects 1–2% of the population. It is caused by white blood cells attacking and destroying the hair follicles (why they do this is unknown). As the name suggests, alopecia areata
involves round spots of hair loss; 80% of people with this condition have only 1 bald spot. A very small percentage of people with alopecia areata
will eventually experience thinning hair everywhere (diffuse alopecia
One clue distinguishing alopecia areata
is the presence of strong pointed hairs on the perimeter of the bald patch that are easy to pull out. Also, the area of bald scalp may appear peach-colored. Alopecia areata
can occur at any age, but the majority get it between the ages of 15 and 29. It might be temporary, particularly if you are older. In 90% of cases, hair grows back on its own; if you are over 40 and have only a small bald spot, it is likely your hair will grow back. Scarring alopecia
occurs when hair follicles are damaged or destroyed. It can be caused by infections, disease, or illness. Hair loss is permanent. Telogen effluvium (TE)
is the tremendous loss of hairs—more than 400 a day—during the resting phase of the hair cycle
. Telogen effluvium may be temporary or chronic, and it can be triggered by any number of emotionally or physiologically stressful events, such as childbirth, chronic illness, surgery, or hormonal changes during menopause.
More Causes of Hair LossChemotherapy
doesn’t just kill cancer cells, it kills any cells that divide rapidly, like cells in the hair follicle
. You can expect to lose 90% of your hair during treatment, but it will start to grow back 6–8 weeks later (it may look and feel different). Within a year, you will have your regular hair back. Radiation
to treat cancer can also cause hair loss in the areas exposed to it. Trichotillomania
is the compulsion to pull out one’s hair. This is more common in women and children than men.
Fluctuations in hormone levels, especially estrogen and thyroid hormone, can cause temporary hair loss. Estrogen prolongs the growth phase of hair. Pregnant women have higher levels of estrogen resulting in thicker and more lush hair. Estrogen levels drop after birth (and again after menopause) and hair goes into the resting phase, which can last up to 6 months. Because hair grows only about 1 cm per month, it can take up to a year for the hair that falls out to grow back again. Breastfeeding mothers may find it takes longer.
Changes in the amount of thyroid hormone produced by your thyroid—too little (hypothyroidism) or too much (hyperthyroidism)—can lead to thinning in different parts of the head.
Hair loss can also be caused by:
- Chronic medical conditions, such as diabetes and lupus—About 50% of people with lupus experience hair loss; it may or may not be permanent.
- Medications—Hair loss can be a side effect of many drugs and medications.
- Diet—nutritional deficiencies, eating disorders and harsh diets result in thinning hair.
- Stress—Your hair is more susceptible to stress than men’s hair.
- Hairstyling and hairstyling products—Excessive pulling and stretching of the hair—in tight ponytails or braids, when straightening it—can lead to permanent hair loss, as can burns from chemical hair relaxers and hot hair irons.