Hair loss, also called alopecia, can occur on any part of the body. Hair loss that occurs on the scalp is generally called baldness. Hair loss is often of great concern to people for cosmetic reasons, but it can also be a sign of a bodywide (systemic) disorder.
Hair grows in cycles. Each cycle consists of a long growing phase (anagen), a brief transitional phase (catagen), and a short resting phase (telogen). At the end of the resting phase, the hair falls out, and the cycle begins again as a new hair starts growing in the follicle. Normally, about 50 to 100 scalp hairs reach the end of resting phase each day and fall out. When many more than 100 hairs/day go into resting phase, hair loss (telogen effluvium) may occur. A disruption of the growing phase causing loss of hairs is called anagen effluvium.
Doctors sometimes classify hair loss as focal (confined to one part of the scalp) or diffuse (widespread).
The most common cause of hair loss is
Other common causes of hair loss are
Less common causes are primary hair shaft abnormalities (that is, the abnormality originates in the hair shaft), sarcoidosis, heavy metal poisoning, radiation therapy, and rare skin conditions.
This form of alopecia eventually affects up to 80% of white men by the age of 70 (male-pattern hair loss) and about half of all women (female-pattern hair loss). The hormone dihydrotestosterone plays a major role, along with heredity. The hair loss can begin at any age during or after puberty, even during the teenage years.
In men, hair loss usually begins at the forehead or on the top of the head toward the back. Some men lose only some hair and have only a receding hairline or a small bald spot in the back. Others, especially when hair loss begins at a young age, lose all of the hair on the top of the head but retain hair on the sides and back of the scalp. This pattern is called male-pattern hair loss.
In women, hair loss occurs on the top of the head and is usually a thinning of the hair rather than a complete loss of hair. The hairline typically stays intact. This pattern is called female-pattern hair loss.
In men, hair is usually first lost at the forehead or on the top of the head toward the back. This pattern is called male-pattern hair loss.
In women, hair is usually first lost on the top of the head. Typically, the hair thins rather than is completely lost, and the hairline stays intact. This pattern is called female-pattern hair loss.
In alopecia areata (see see Alopecia Areata), round, irregular patches of hair are suddenly lost. The cause is believed to be an autoimmune reaction.
Systemic lupus erythematosus (lupus), an autoimmune disorder, affects various organs throughout the body. When the skin is affected, the disorder is called cutaneous lupus. If skin lesions affect the scalp or hair follicles, areas of hair may be lost. Hair loss may be permanent if the hair follicle is completely destroyed.
If women have excessive amounts of male hormones, they can develop masculine characteristics (called virilization), such as a deepened voice, acne, and hair in locations more typical of male hair growth, such as the face and trunk (hirsutism—see Hairiness). Virilization can also include hair loss in the typical male pattern. The most common cause of virilization is polycystic ovary syndrome. Rarely, a tumor can secrete male hormones, causing virilization, or virilization may develop in a female who is taking anabolic steroids to enhance athletic performance.
Hair loss can also occur after childbirth or during menopause.
Drugs: Male or female-pattern baldness can occur when anabolic steroids are used. It can also occur frequently with the use of chemotherapy drugs.
Nutritional disorders are a less common cause of hair loss. Symptoms vary according to the specific nutritional disorder:
Stresses such as a high fever, surgery, a major illness, weight loss, or pregnancy can increase the number of hairs that go into the resting phase (causing telogen effluvium). Hair typically falls out a few months after the stress. This type of hair loss tends not to be permanent.
These stresses include the habitual pulling out of normal hair (trichotillomania). The habit is most common among children but may occur in adults. The hair pulling may not be noticed for a long time, confusing doctors and parents, who may mistakenly think that a disorder such as alopecia areata or a fungal infection is causing the hair loss.
Ringworm of the scalp (tinea capitis):
This fungal infection is a common cause of patchy hair loss in children. The infection begins as a red patch with scaling that gradually enlarges. Hairs may eventually break off, usually flush with the scalp, looking like black dots. Sometimes parts of the hair remain above the scalp. Hair loss may be permanent, especially if the infection is left untreated.
This disorder is hair loss caused by tight braids, rollers, or ponytails that pull constantly on hair. Hair loss most often occurs at the hairline of the forehead and temples.
The following information can help people decide whether a doctor's evaluation is needed and help them know what to expect during the evaluation.
The following are of particular concern:
When to see the doctor:
People who have hair loss and signs of a bodywide disorder or poisoning should see a doctor within a day or two. Women who have developed masculine characteristics should see a doctor within a week or so. Other people should see a doctor when possible, but an appointment is not urgent unless other symptoms develop.
What the doctor does:
Doctors first ask questions about the person's symptoms and medical history and then do a physical examination. What doctors find during the history and physical examination often suggests a cause and the tests that may need to be done.
Doctors ask about the hair loss:
They note other symptoms such as itching and scaling. They ask about hair care, including whether braids, rollers, and hair dryers are used and whether the hair is routinely pulled or twisted.
Doctors ask whether the person has been recently exposed to drugs, toxins, or radiation or has experienced significant stress (such as that from surgery, chronic illness, or fever or psychologic stress). The person is asked about other characteristics that may suggest a cause, including dramatic weight loss, dietary practices (including vegetarianism), and obsessive-compulsive behavior. Current and recent drug use is reviewed. The person is asked whether any family member has had hair loss.
During the physical examination, doctors focus on the scalp, noting the distribution of hair loss, the presence and characteristics of any skin abnormalities, and the presence of any scarring. They measure the width of the part and check for abnormalities of hair shafts.
Doctors evaluate hair loss elsewhere on the body (such as the eyebrows, eyelashes, arms, and legs). They look for rashes that may be associated with certain types of alopecia and for signs of virilization in women, such as a deepened voice, hirsutism, an enlarged clitoris (the smaller female organ that corresponds to the penis), and acne. They also examine the thyroid gland.
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Testing is usually unnecessary if a cause is identified based on the doctor's examination. For example, male-pattern and female-pattern hair loss generally requires no testing. However, if hair loss occurs in a young man with no family history of hair loss, the doctor may question him about anabolic steroid use and other drugs. If women have significant hair loss and have developed masculine characteristics, blood tests are done to measure levels of the hormones testosterone and dehydroepiandrosterone sulfate (DHEAS). If the doctor's examination detects signs of other hormonal abnormalities or other serious illness, blood tests to identify those disorders may be needed.
The pull test helps doctors evaluate hair loss. Doctors gently pull on a bunch of hairs (about 40) on at least 3 different areas of the scalp. Doctors then count the number of hairs that come out with each pull and examine them under a microscope to determine their phase of growth. If more than 4 to 6 hairs in the telogen phase come out with each pull, the pull test is positive, and the person most likely has telogen effluvium.
During the pluck test, doctors abruptly pull out about 50 individual hairs (“by the roots”). Doctors examine the roots and shafts of the plucked hairs under a microscope to assess the hair shaft and determine the phase of growth. These results help doctors tell whether the person has a telogen effluvium, a primary hair shaft abnormality, or some other problem.
Daily hair counts can be done to quantify hair loss when it is not clear whether hair loss is actually excessive. Hairs lost in the first morning combing or during washing are collected in clear plastic bags daily for 14 days. The number of hairs in each bag is then recorded. Loss of more than 100 hairs/day is abnormal except after shampooing, when up to 250 hairs may be lost. Hairs may be brought in by the person for examination under a microscope.
A biopsy of the scalp skin (see Diagnosis of Skin Disorders) is done if the diagnosis is not clear after a doctor's examination and other tests. A biopsy helps determine whether hair follicles are normal and can help differentiate alopecia that causes scarring (by destroying the hair follicle) from alopecia that does not. If the hair follicles are abnormal, the biopsy may indicate possible causes.
Specific causes of hair loss are treated when possible. For example, antifungal drugs are used to treat scalp ringworm. Drugs that are causing hair loss are switched or stopped. Hormonal disorders can be treated with drugs or surgery, depending on the cause. Iron or zinc supplements can be given if these minerals are deficient. Cutaneous lupus and lichen planopilaris can usually be treated with corticosteroids or other drugs applied to the scalp or taken by mouth.
Traction alopecia is treated by eliminating physical traction or stress to the scalp.
Scalp ringworm is treated with antifungal drugs taken by mouth.
Trichotillomania is difficult to treat, but behavioral modification, clomipramine, or a selective serotonin reuptake inhibitor (such as fluoxetine, fluvoxamine, paroxetine, sertraline, escitalopram, or citalopram) may be useful.
Hair loss due to physical stresses such as recent weight loss, surgery, a severe illness with a fever, or delivery of a baby (telogen effluvium) is not typically treated because it tends to resolve on its own. Applying minoxidil to the scalp may be helpful for some people.
If hair does not regrow on its own, hair replacement methods can be tried, including
Male-pattern and female-pattern hair loss can sometimes be treated effectively with drugs.
Minoxidil may prevent further hair loss and increase hair growth when applied directly to the scalp twice a day. Hair regrowth can take 8 to 12 months and is noticeable in only about 30 to 40% of people. The most common side effect is skin irritation, such as itching and rash.
Finasteride works by blocking the effects of male hormones on the hair follicles and is taken by mouth daily. Finasteride is not used in women who have hair loss. In men, its effectiveness at stopping hair loss and stimulating hair growth is usually evident within 6 to 8 months of treatment and increases over time. After 2 years of treatment, about 66% of men have noticeable hair regrowth. Finasteride can decrease libido, increase breast size, and contribute to erectile dysfunction. Finasteride can also decrease prostate-specific antigen levels. Men should discuss how finasteride can affect prostate cancer screening with their doctor before they begin treatment.
The most important effect of minoxidil or finasteride may be to prevent further hair loss. The effects last only as long as the drugs are taken.
Hormonal modulators, such as birth control pills (oral contraceptives) or spironolactone, may be useful in some women, especially those who have developed masculine characteristics.
Transplantation is a more permanent solution. In this procedure, hair follicles are removed from one part of the scalp and transplanted to the bald area. In a newer hair transplantation technique, only one or two hairs are transplanted at a time. Although this technique is more time-consuming, it does not require removal of large plugs of skin and allows the implants to be oriented in the same direction as the natural hair.
Another surgical option involves removing some bald parts of the scalp skin and stretching the parts that have hair over a wider area.
Wigs often offer the best treatment for temporary hair loss (for example, that caused by chemotherapy). People undergoing chemotherapy should consult a wig maker even before therapy begins so that an appropriate wig can be ready when needed.
Alopecia areata is sudden loss of patches of hair when there is no obvious cause such as a skin or general bodywide disorder.
Alopecia areata is common. It occurs in both sexes and at all ages but is most common among children and young adults. The cause is believed to be an autoimmune reaction in which the body's immune defenses mistakenly attack the hair follicles. Alopecia areata is not the result of another disorder, but some people may also have a thyroid disorder or vitiligo (a skin pigment disorder).
Round, irregular patches of hair are suddenly lost. Around the edges of the patches are characteristic short, broken hairs, which resemble exclamation points. The site of hair loss is usually the scalp or beard. Rarely, all body hair is lost (a condition called alopecia universalis). The hair usually grows back in several months. In people with widespread hair loss, regrowth is less likely.
Alopecia areata can be treated with corticosteroids. For small bald patches, corticosteroids are typically injected under the skin of the bald patch, and minoxidil may be applied topically as well. For larger patches, corticosteroids can be applied to the scalp (topically) or, more rarely, taken by mouth. Another treatment for alopecia areata involves applying irritating chemicals, such as anthralin or diphenylcyclopropenone, to the scalp to induce a mild allergic reaction or irritation. The irritation sometimes promotes hair growth.
Last full review/revision September 2012 by Wendy S. Levinbook, MD