Hair loss, also called alopecia, is a disorder caused by an interruption in the body’s cycle of hair production. Hair loss can occur anywhere on the body, but most commonly affects the scalp. On average, the scalp has 100,000 hairs that cycle through periods of growing, resting, falling out, and regenerating.
A hair growth cycle consists of three phases. During the anagen phase, hair grows actively. This phase may last for years. During the catagen phase, hair stops growing and separates from its follicle, which is the structure beneath the skin that holds the hair in place. The catagen phase lasts about 10 days. During the telogen phase, the follicle rests for two or three months, and then the hair falls out. The next anagen phase begins as a new hair grows in the same follicle. Most people lose 50 to 100 hairs per day as part of this natural cycle.
If this cycle is disrupted, or if a hair follicle is damaged, hair may begin to fall out more quickly than it is regenerated, leading to symptoms such as a receding hairline, hair falling out in patches, or overall thinning.
Hair loss may be linked to a person’s genetics, although many medical and behavioral conditions may interrupt the growth cycle and cause hair loss. At NYU Langone, dermatologists specialize in hair and scalp disorders and can identify the type of hair loss, as well as its cause.
Androgenetic alopecia is the most common type of hair loss, affecting more than 50 million men and 30 million women in the United States. Commonly known as male pattern hair loss or female pattern hair loss, androgenetic alopecia is hereditary but can be managed with medication or surgery.
In men, hair loss can begin any time after puberty and progress over the course of years or decades. It starts above the temples and continues around the perimeter and the top of the head, often leaving a ring of hair along the bottom of the scalp. Many men with male pattern hair loss eventually become bald.
In women, hair slowly thins all over the scalp, but the hairline usually doesn’t recede. Many women experience this type of hair loss as a natural part of aging, although hair loss may begin any time after puberty. Female pattern hair loss can cause hair to thin dramatically, but only rarely does it lead to baldness.
Telogen effluvium, a type of hair loss, occurs when large numbers of follicles on the scalp enter the resting phase of the hair growth cycle, called telogen, but the next growth phase doesn’t begin. This causes hair to fall out all over the scalp without new hair growth.
Telogen effluvium does not generally lead to complete baldness, although you may lose 300 to 500 hairs per day, and hair may appear thin, especially at the crown and temples.
A medical event or condition, such as a thyroid imbalance, childbirth, surgery, or a fever, typically triggers this type of hair loss. Telogen effluvium may also occur as a result of a vitamin or mineral deficiency—iron deficiency is a common cause of hair loss in women—or the use of certain medications, such as isotretinoin, prescribed for acne, or warfarin, a blood thinner. Starting or stopping oral contraceptives (birth control pills) may also cause this type of hair loss.
Telogen effluvium usually begins three months after a medical event. If the triggering event is temporary—for example, if you recover from an illness or stop taking the medication causing the hair loss—your hair may grow back after six months. Telogen effluvium is considered chronic if hair loss lasts longer than six months.
For reasons that are unclear to doctors, this type of hair loss may last for years in some people. If hair doesn’t regrow on its own, our dermatologists can offer medication that can help.
Anagen effluvium is rapid hair loss resulting from medical treatment, such as chemotherapy. These potent and fast-acting medications kill cancer cells, but they may also shut down hair follicle production in the scalp and other parts of the body. After chemotherapy ends, hair usually grows back on its own. Dermatologists can offer medication to help hair grow back more quickly.
Alopecia areata is an autoimmune condition, which means the body’s immune system attacks healthy tissues, including the hair follicles. This causes hair to fall out and prevents new hair from growing.
This condition can affect adults and children, and hair loss can begin suddenly and without warning. Hair from the scalp typically falls out in small patches and is not painful. Hair in other parts of the body, including the eyebrows and eyelashes, may also fall out. Over time, this disease may lead to alopecia totalis, or complete hair loss.
Dermatologists treat alopecia areata with medication that may help hair regrow. If you are interested in talking with other people who have alopecia areata, NYU Langone hosts a monthly support group for people with this condition.
Tinea capitis, also called scalp ringworm, is a fungal infection of the scalp that’s a common cause of hair loss in children. This condition causes hair to fall out in patches, sometimes circular, leading to bald spots that may get bigger over time.
The affected areas often look red or scaly, and the scalp may be itchy. Sores or blisters that ooze pus can also develop on the scalp. A child with the condition may have swollen glands in the back of the neck or a low-grade fever as a result of the immune system fighting the infection.
Dermatologists can prescribe an antifungal medication taken by mouth to eliminate the fungus. If tinea capitis is diagnosed and treated early, most children have excellent hair regrowth.
Cicatricial alopecia, also known as scarring alopecia, is a rare type of hair loss in which inflammation destroys hair follicles and causes scar tissue to form in their place. After scar tissue forms, hair doesn’t regrow.
Hair loss may begin so slowly that symptoms aren’t noticeable, or hair may start to fall out all at once. Other symptoms include severe itching, swelling, and red or white lesions on the scalp that may resemble a rash. This type of hair loss can occur at any age and affects men and women.
Treatment depends on the type of cicatricial alopecia causing your symptoms. Our doctors have years of experience treating people with cicatricial alopecia and can recommend a variety of treatments to help you. Types of cicatricial alopecia include:
Lichen planopilaris, a type of alopecia, occurs when a common skin condition, called lichen planus, affects the scalp. Lichen planopilaris may cause a dry, flaky rash to appear on the skin that causes hair on the scalp to fall out in clumps. The scalp may also become red, irritated, and covered in small white or red itchy, painful, or burning bumps.
Lichen planopilaris is not common and affects more women than men. A doctor may prescribe medication to stop the hair loss.
Discoid lupus erythematosus is a type of cutaneous lupus, an autoimmune disease that affects the skin. It can lead to inflamed sores and scarring on the ears, face, and scalp. Hair loss is one symptom of the disease. When scar tissue forms on the scalp, hair can no longer grow in that area.
Hair loss caused by folliculitis decalvans, an inflammatory disorder that leads to the destruction of hair follicles, is often accompanied by redness, swelling, and lesions on the scalp that may be itchy or contain pus, known as pustules. This type of hair loss is not reversible, but dermatologists can offer medication to control symptoms and, in some instances, stop the progression of hair loss.
Dissecting cellulitis of the scalp, a rare condition, causes pustules or lumps to form on the scalp. This condition may also cause scar tissue to develop, destroying hair follicles and causing hair loss. Medications may help control symptoms.
Frontal fibrosing alopecia typically occurs in a receding hairline pattern and may also result in hair loss in the eyebrows and underarms. Frontal fibrosing alopecia most commonly affects postmenopausal women. Certain medications can manage symptoms and stop the progression of the disease. The cause is unknown.
Central centrifugal cicatricial alopecia may occur as a result of hair products or styling techniques that damage hair follicles. The use of hair relaxers, blow dryers, curling irons, and hair extensions can cause central centrifugal cicatricial alopecia, as can the process of creating a permanent wave, or a “perm.”
The frequent application of oils, gels, or pomades can also cause this condition, which may be reversible if you stop using these hair products or styling techniques. Our dermatologists may recommend taking medication to help hair grow back.
Several types of hair shaft abnormalities can lead to hair loss. These conditions cause strands of hair to thin and weaken, making them vulnerable to breaking. The hair loss doesn’t occur in the follicle but as a result of a break somewhere along the hair shaft, which is the visible part of a hair strand. This can result in overall thinning, as well as in many small, brittle hairs.
Making simple changes to the way you style and treat your hair can reverse some hair shaft abnormalities. Other conditions may require medical intervention. Types of hair shaft abnormalities include:
Loose anagen syndrome, which most commonly presents in young children, occurs when hair that is not firmly rooted in the follicle can be pulled out easily. Most of the time, hair falls out after it has reached an arbitrary maximum length. Children with loose anagen syndrome often cannot grow hair beyond a relatively short length. The condition more commonly affects girls with blond or brown hair.
In people who have loose anagen syndrome, hair can fall out easily—even when it’s growing. For example, hair loss may accelerate overnight because of the friction of a pillow. The cause of loose anagen syndrome is unknown, though it may be related to a disorder in the hair growth cycle that prevents hair from staying in the follicle.
There are few reliable treatments, but the condition tends to improve greatly with puberty, and some medications may result in fuller hair.
People with trichotillomania pull their hair out and find it difficult to stop. This results in hair loss on the scalp or elsewhere on the body. Hair often returns if the behavior is stopped, but hair loss can be permanent if the pulling continues for many years.
The best treatment for this condition may be psychotherapy, which might include talking with a counselor about causes of stress and why you feel the urge to pull your hair. Our doctors can refer you to a psychotherapist who specializes in this condition.
Some hairstyles, including tight ponytails and braids, pull hair away from the scalp with such force that hair strands are damaged and fall out. Unless the hairstyle is changed, traction alopecia may lead to thinning hair or bald spots. Most of the time, hair regrows after you alter the hairstyle.
Hypotrichosis is a rare genetic condition in which very little hair grows on the scalp and body. Babies born with this condition may have typical hair growth at first; however, their hair falls out a few months later and is replaced with sparse hair.
Many people with hypotrichosis are bald by age 25. There are few treatment options for this condition, but some medications may help to thicken or regrow hair.