Hair Loss Types and Symptoms, Causes, Risk Factors
Interesting Facts About Hair and Hair Loss
- The average human scalp has about 100,000 hairs.
- People with blond hair typically have more hair (average 140,000 hairs) than the average brunette (105,000 hairs) or redhead (90,000).
- About 90% of a person's scalp hair is in a continual growth phase that lasts two to six years.
- The other 10% of scalp hair is in a resting phase that lasts between two and three months.
- Hair grows faster in warm weather than in cold.
- Hair grows at an average rate of 1 centimenter (around half an inch) per month.
- Between 70 and 150 hairs are regularly lost from the scalp each day.
- About 40% of the density of scalp hair has to be lost before thinning of the hair becomes noticeable.
- Shaving hair does not stimulate hair growth.
- Hair plucking does not stop hair growth.
How much hair you have on your body and head is determined by your genes. Every hair grows within a hair follicle, which is a tiny tube of cells close to the surface of the skin. Each hair has a root and a shaft within this follicle. The hair shaft contains no living tissue. It consists of protein material twisted into a very fine rope-like arrangement. It is this part of the structure that we think of in everyday terms as "hair." The hair root does not grow continuously, three phases of the hair growth cycle exist: anagen (growth phase), catagen (degradation phase), and telogen (resting phase).
Human hairs are randomly distributed all over the scalp in terms of their growth pattern. Approximately 85 to 90 percent of hair follicles are in the anagen phase of hair growth. Each day the hair grows approximately 0.35 mm (6 inches per year). Follicles remain in this phase for an average of three years (range, two to six years). Catagen phase (two to four weeks) of follicular regression follows, usually affecting 2 to 3 percent of hair follicles. Finally, the telogen phase occurs, during which 10 to 15 percent of hair follicles undergo a rest period for about three months. At the conclusion of this phase, the inactive hair is ejected from the skin. The cycle is then repeated.
On average 50-100 telogen hairs are shed every day. This is normal hair loss and accounts for the hair loss seen every day in the shower and with hair combing. These hairs will regrow. A variety of factors can affect the hair growth cycle and cause temporary or permanent hair loss including medication, radiation, chemotherapy, exposure to chemicals, hormonal and nutritional factors, thyroid disease, generalized or local skin disease, and stress.
However, almost everyone experiences some hair loss with aging. The rate of hair growth slows. The hair strands become smaller and have less pigment, so the thick, coarse hair of a young adult eventually becomes thin, fine, light-colored hair. Many hair follicles stop producing new hairs altogether.
The word "alopecia" is the medical term for hair loss. Alopecia does not refer to one specific hair loss disease -- any form of hair loss is an alopecia. The word alopecia is Latin, but can be traced to the Greek "alopekia," which itself comes from alopek, meaning "fox." Literally translated, the word alopecia (alopekia) is the term for mange in foxes.
The are different types of hair loss. The main types are as follows:
| Type of hair loss | Description |
|---|---|
| Androgenetic alopecia | Balding caused by heredity. It can affect both men and women, although women with this inherited tendency do not become totally bald. The condition can start in a person's teens, twenties, or thirties. |
| Telogen effluvium | Loss of a considerable amount of hair in a short time, usually in response to a stressful situation, medication, medical treatment, or illness |
| Alopecia areata | Loss of small round or oval patches of hair. It usually clears completely within 6 to 12 months without treatment. |
| Trichotillomania | The urge to pull hair from the scalp or other parts of the body |
| Alopecia totalis | An uncommon condition in which all hair on the scalp is lost. The cause is unknown, and the baldness is usually permanent. |
| Alopecia universalis | A total loss of hair on all parts of the body. |
| Traction alopecia | Hair loss caused by chronic traction on the hair follicle. Occurs often in people who wear tight braids or cornrow hair styles. |
Androgenetic alopecia is an extremely common disorder affecting both men and women. In men, this condition is also known as male-pattern hair loss.
In the word androgenetic - "andro" refers to the androgens (testosterone, dihydrotestosterone) necessary to produce male-pattern hair loss (MPHL), "genetic" refers to the inherited gene necessary for MPHL to occur. In men who develop male pattern baldness the hair loss may begin any time after puberty when blood levels of androgens rise.
Androgenetic alopecia accounts for more than 95% of hair loss in men and affects roughly 50% of men and perhaps as many women older than 40 years. As many as 13% of premenopausal women reportedly have some evidence of androgenetic alopecia. However, the incidence increases greatly in women following menopause, and, according to one author, it may affect 75% of women older than 65 years.
The incidence and the severity of androgenetic alopecia tend to be highest in white men, second highest in Asians and African Americans, and lowest in Native Americans and Eskimos.
Hamilton and later Norwood have classified the patterns of male pattern baldness
In men hair is lost in a well-defined pattern, beginning above both temples. Over time, the hairline recedes to form a characteristic "M" shape. Hair also thins at the crown (near the top of the head), often progressing to partial or complete baldness. In general, those who begin losing hair in the second decade are those in whom the hair loss will be the most severe. In some men, initial male-pattern hair loss may be delayed until the late third to fourth decade. It is generally recognized that men in their 20’s have a 20 percent incidence of male pattern baldness, in their 30’s a 30 percent incidence of male pattern baldness, in their 40’s a 40 percent incidence of male pattern baldness, etc. Using these numbers one can see that a male in his 90’s has a 90 percent chance of having some degree of male pattern baldness.
The pattern of hair loss in women differs from male-pattern baldness. In women, the hair becomes thinner all over the head, and the hairline does not recede. Androgenetic alopecia in women rarely leads to total baldness.
In androgenetic alopecia, the genes (AR gene) affect how the hair grows. They trigger a sensitivity to a class of hormones called androgens, particularly an androgen called dihydrotestosterone (DHT). Androgens are important for normal male sexual development before birth and during puberty. Androgens also have other important functions in both males and females, such as regulating hair growth and sex drive. Hair follicles that are sensitive to DHT begin to miniaturize, shortening the lifespan of each hair follicle affected. Eventually, these affected follicles stop producing cosmetically acceptable hair. The progression of the disorder is stopped if postpubertal males are castrated, also it is not found in males castrated prior to puberty.
Telogen effluvium (TE) is probably the second most common form of hair loss dermatologists see. It is a poorly defined condition; very little research has been done to understand TE. Though, it is known that TE is caused by shifting of large percentage of scalp hair follicles into the telogen phase of hair growth. The cause of this abnormally timed telogen phase may be hormonal, nutritional, drug-related or associated with stress. The disproportionate shedding leads to a decrease in the total number of hairs. Axillary and pubic areas often are involved, as well as the scalp.
TE appears as a diffuse thinning of hair on the scalp. Most often, the hair on top of the scalp thins more than it does at the sides and back of the scalp. There is usually no hair line recession, except in a few rare chronic cases. People with TE never completely lose all their scalp hair, but the hair can be noticeably thin in severe cases. While TE is often limited to the scalp, in more serious cases TE can affect other areas, like the eyebrows or pubic region. Whatever form of hair loss TE takes, it is fully reversible. The hair follicles are not permanently or irreversibly affected; there are just more hair follicles in a resting state than there should normally be.
Alopecia areata (AA) is the next most common form of hair loss, after androgenetic alopecia and telogen effluvium. Alopecia areata (AA) is a recurrent disease, which can cause hair loss in any hair-bearing area. AA can affect men, women, and children. It often appears as well-defined circular bald patches on the scalp. The patch is usually smooth bald skin with nothing obvious to see beyond the absence of hair. Many people will get just one or two patches, but for some the hair loss can be extensive. The hair loss can be quite sudden, developing in a matter of a few days and it may happen anywhere on the scalp. Children who develop AA before puberty are most likely to develop more extensive and persistent hair loss.
The cause of alopecia areata is unknown but commonly thought to be an autoimmune disorder (the body does not recognize the hair follicles and attacks them). Stress and anxiety are frequently blamed by patients as the cause of their hair loss. The inflammation involved in AA focuses on the roots of hair follicles deep in the skin. As a result there is very little visible at the skin surface. There is no redness and often no pain, although a few people do find their skin itchy or painful to touch in the very early stages of AA development. The hair follicles, are not completely destroyed and can re-grow if the inflammation subsides. People with just one or two patches of AA often have a full and spontaneous recovery within two years whether or not they receive treatment. However, about 30% of individuals find the condition persists and becomes more extensive, or they have repeated cycles of hair loss and re-growth.
Hair loss that spreads to cover the entire scalp is called alopecia totalis. If it spreads over the entire body, affecting scalp, eyebrows, lashes, beard, pubic hair, and everything else, then the condition is called alopecia universalis. If the alopecia is just limited to the beard area in men, it is called alopecia barbae. The hair usually grows back within 6 months to one year. Most patients will suffer episodes of hair loss in the same area in the future.
Trichotillomania is the name given to habitual, compulsive plucking of hair from the scalp or other hair-bearing areas of the body. Long-term trichotillomania can result in permanent damage to scalp skin and to scarring alopecia. In its mildest form, trichotillomania is a habitual plucking of hair while a person reads or watches television. In its more severe forms, trichotillomania has a ritualistic pattern and the hair-plucking may be conducted in front of a mirror.
The mean age of onset of trichotillomania is eight years in boys and 12 years in girls, and it is the most common cause of childhood alopecia. Although any part of the body can be involved, the scalp is the most common. Patients also may eat the plucked hairs (trichophagy), causing internal complications such as bowel obstruction.
Traction alopecia is caused by chronic traction (pulling) on the hair follicle. It often occurs in persons who wear tight braids or cornrow hair styles that lead to high tension and breakage in the outermost hairs. Traction alopecia also occurs commonly in female athletes who pull their hair tightly in ponytails. Men who attach hairpieces to their existing hair can experience this type of permanent hairloss if the hairpiece is attached in the same location over a long period of time.
Hair loss due to scarring of the scalp is called scarring alopecia. Scarring can be due to a variety of causes. Traction alopecia and trichotillomania over a period of time may lead to scarring and permanent hair loss. Injury to the scalp caused by physical trauma or burns may leave permanent scars and permanent hair loss. Diseases that may cause permanent hair loss due to scalp scarring include the autoimmune conditions lupus erythematosus and scleroderma, and bacterial infections such as folliculitis, fungal infections, and viral infections such as shingles (herpes zoster).
The cause of triangular alopecia (alopecia triangularis) is not known. It is usually apparent from birth and tends to affect a triangular patch of skin and hair above the temples. For unknown reasons, the skin fails to grow hair follicles in this area in a few people. If hair loss is not complete, the remaining hairs are often "miniaturized"-fine-textured hairs of thin diameter. The affected area can be surgically removed or implanted with hair follicles taken from elsewhere on the scalp.
Loose-anagen syndrome occurs most frequently in fair-haired persons. During the growth cycle, scalp hairs sit so loosely in the follicles from which they grow that they can be easily extracted by combing or brushing. The condition may appear in childhood and gradually improve or disappear over time.
It is normal to lose between 50-100 hairs a day, this is part of the hair renewal process. However most people suffer from excessive hair loss at one time in their life. There are many reasons for this including medication, radiation, chemotherapy, exposure to chemicals, hormonal and nutritional factors, thyroid disease, generalized or local skin disease, and stress.
Since hormones both stimulate hair growth and cause hair loss, hormonal
changes by far have the biggest impact on hair loss. Hormonal changes can
affect both men and women. This type of hair loss is caused by the androgen
DHT, or Dihydrotestosterone. Since everyone has DHT that is produced by
their bodies and only some people suffer from hair loss there has to be
another factor involved. This other factor is having follicles that have
a greater number of Androgen receptors for the DHT to attach to. This is
the component that is inherited through the genes.
Childbirth
After pregnancy many women experience a loss of hair, which is caused by
many hair simultaneously entering the resting phase, which in turn is caused
by the hormonal changes that take place after a woman's body recovers from
her pregnancy. Within two to three months after giving birth, some women
will notice large amounts of hair coming out in their brushes and combs.
This can last one to six months, but resolves completely in most cases.
ome women experience an increase in hair loss several months after delivering
a baby. This is because during pregnancy the hair is shifted into an active
growth state that then goes back to baseline soon after delivery. This increased
hair loss usually corrects itself.
Birth control pills
Women who have a genetic predisposition for androgenic alopecia can have
it occur at a much younger age by taking birth control pills. The hormonal
changes that occur trigger the onset of the androgenic alopecia. If there
is a history of female pattern loss in the family, she should advise her
doctor before going on the pill. After the discontinuation of the pill the
woman may notice that her hair begins shedding two or three months later.
This may continue for six months when it usually stops. In some cases the
process cannot be reversed and the woman may not regrow some of the hair
that was lost.
Since the follicle is a very sensitive it does respond to imbalances in the body. Most hair loss causes by disease or illness is temporary and resolves itself after the body has returned to a healthy condition.
High Fever, Severe Infection, Severe Flu
Sometimes one to three months after a high fever, severe infection or flu,
a person may experience temporary hair loss, that usually corrects itself.
Diabetes, Lupus, Thyroid disease
Diabetes, lupus, and both an overactive thyroid and an underactive thyroid
can cause hair loss which can be reversed with proper treatment.
Deficient Diet
Some people who go on low protein diets, or have severely abnormal eating
habits, may develop protein malnutrition. To help save protein the body
shifts growing hair into the resting phase. If this happens massive amounts
of hair shedding can occur two to three months later. A sign of this is
if the hair can be pulled out by the roots fairly easily. This condition
can be reversed and prevented by eating the proper amount of protein.
Medications
Some prescription drugs may cause temporary hair shedding in a small percentage
of people. Examples of such drugs include some of the medicines used for
the following: gout, arthritis, depression, heart problems, high blood pressure,
or blood thinner. High doses of vitamin A may also cause hair shedding.
Cancer Treatments
Chemotherapy and radiation treatment will cause hair loss because it stops
hair cells from dividing. Hairs become thin and break off as they exit the
scalp. This occurs one to three weeks after the treatment. Patients can
lose up to 90 percent of their scalp hair. The hair will regrow after treatment
ends. There are some drugs in development to help prevent this hair loss
from occurring.
Low Serum Iron
Iron deficiency occasionally produces hair loss. Some people don't have
enough iron in their diets or may not fully absorb iron in their diets.
Women who have heavy menstrual periods may develop iron deficiency.
Major Surgery/Chronic Illness
Anyone who has a major operation may notice increased hair shedding within
one to three months afterwards. The condition reverses itself within a few
months but people who have a severe chronic illness may shed hair indefinitely.
A relatively unknown fact is that hair transplantation surgery can actually
cause additional hair loss or "shock fallout". Hairs lost from shock fallout
usually don't regrow.
Alopecia Areata
This type of hair loss is believed to be caused by the immune system reacting
to hair follicles as if they were antibodies and shutting them down. The
hair loss is usually limited to a coin sized area and all the hair in the
area is lost leaving a totally smooth round patch.
Fungus Infection (Ringworm) of the Scalp
Caused by a fungus infection, ringworm begins with small patches of scaling
that can spread and result in broken hair, redness, swelling, and even oozing.
This contagious disease is most common in children. Once infections are
treated, hair generally regrows. Ringworm can usually be treated with a
topical or oral antifungal medication.
Stress
Stress can cause hair loss in some people. Usually it occurs 3 months after
the stressful event has occured and it may take 3 months after the stress
period has ended for the hair growth to resume. In most cases it is temporary,
but if the person is predisposed to androgenic alopecia, the stress may
trigger the onset of genetic hair loss or may worsen existing androgenic
hair loss.
Damage to the hair can be self inflicted either by intentional or unintentional means. Styling hair by bleaching, braiding and straightening can cause damage and results in hair being lost.
Trichotillomania or Hair Pulling
Some children and less often adults play with their hair by pulling on it
or twisting it. This can be part of a behavioral problem or a bad habit
that is often done unconsciously. If the behavior is not stopped permanent
hair loss can result from the constant stress on the hair.
Hair Styling Treatments
Many people change the appearance of their hair by using chemical treatments
like dyes, tints, bleaches, straighteners, relaxers and permanent waves.
These products can cause hair to become damaged and break off if they are
overused or used incorrectly. Some chemical relaxers do contain powerful
chemicals and there have been instances of people get chemical burns from
these products resulting in permanent hair loss.
Hair Braids/Weaves
Many black women and some black men braid their hair or wear hair weaves.
Under normal conditions these cause no problems. However if the weave is
attached too tight or the braids are wrapped too tight, they put a constant
strain on the hair follicle. If this is done for an extended period of time
permanent hair loss can result.
Infancy
It's also common for babies to lose a patch of hair on the back of their
heads from rubbing against mattresses, playpens and car seats. Hair will
grow back once a baby begins to spend more time sitting up.
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