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Causes & Types of Alopecia

Androgenetic alopecia

Alopecia Androgenetica is the most common type of hair loss in both sexes. Male pattern baldness is a common name in English language that describes exactly this gradual affection of some areas on the scalp, while some others remain intact. This alopecia is caused by the gradual conversion of terminal to vellus hair, only in those scalp follicles that have the genetic potential to be inhibited by androgens over a period of time, different for each individual. The hair follicles most typically subject to alopecia androgenetica are in the temporofrontal and crown regions of the scalp.

Consequently, the biological behaviour of the scalp hairs is not identical for each one of them. Some are genetically programmed to fall off prematurely, while others are programmed to remain in the scalp area for life.

hough male pattern baldness is treatable, it cannot be cured as it is genetically predetermined. The DHI global network and its hair diagnostic procedures (medical and dermatological examinations, DHI alopecia test, etc.) are essential in precisely defining the type of hair loss. A great result is possible only if a correct diagnosis has been pre-established.

In the word ‘adrogenetic’, the part “Andro” refers to the androgens (testosterone, dihydrotestosterone) that must be present in order for the male–pattern hair loss to appear (MPHL) and the part “genetic” refers to the inherited genes necessary for the MPHL phenotype to be expressed. These genes can get inherited either from the mother’s or the father’s side.

In men who develop male pattern baldness, the hair loss may usually start any time after puberty when the blood androgens’ levels rise. The first change is usually recession at the temporal areas, which is seen in 96% of mature Caucasian males, regardless of the final development of the hair loss. Still there are cases where the hair loss starts in elder ages (in the thirties) and these have usually a different development concerning distribution and grade of baldness.

Alopecia Areata

Alopecia Areata (AA) is a recurrent disease which can cause hair loss in any hair-bearing area. It usually appears as a single oval patch or multiple confluent patches of asymptomatic, well-circumscribed, non-scarring alopecia. Severity varies from a small bare patch to loss of hair on the entire scalp. So-called “exclamation point” hairs are a hallmark of the disorder. These hairs are usually located at the periphery of the patch and extend several millimetres above the scalp.

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 but AA is a disorder with genetic predisposition. The hair usually grows back within 6 months to one year [80 -90% of cases]. Most patients will suffer episodes of hair loss in the same area in the future.

Alopecia areata occurs in 2% of the general population, with men and women equally affected. The condition may be present in persons of any age, but is more common in children and young adults.

The course of alopecia areata is one of spontaneous remissions and recurrences. Although patients with this disorder are usually otherwise healthy, some have co morbid conditions such as atopy, thyroid disease, or vitiligo. Alopecia areata has been strongly associated with certain human leukocyte antigen class II alleles.

There are a few types of AA according to its development: the localized scalp AA, the facial AA (prefers eyebrows and beard), the diffuse AA, the ophiasis type (extended localized), the alopecia totalis (affects the whole scalp) and the alopecia universalis (complete loss of all the body hairs).

Cicatricial Alopecia

  • Hair growth disorders (genetic problems)
  • Lichen planus pilaris
  • Discoid lupus erythematosus
  • Neoplasm
  • Local trauma
  • Folliculitis decalcitrans
  • Scleroderma
  • Pseudopelade of Broque
  • Traction alopecia
  • Trichotillomania
  • Bacterial or fungal infections
  • Cosmetic alopecia (wigs or chemical factors)

Transplantation of hair follicles in areas with scar tissue has a differentiated success in hair regrowth. Nevertheless, it is recommended that the local disease that caused the scarring alopecia should be in recession and of steady appearance at least for a year in order to try local hair restoration. Still, on one hand, there is always the risk of remission of the disease after the session and, on the other hand, the final hair growth percentage may possibly be lower than the expected one.

Traumatic Alopecia

Alopecia from damage to hair follicles.

Cicatricial alopecia is hair loss resulting from a condition that damages the scalp and hair follicle. In addition to a bald spot, the scalp usually has an abnormal appearance. Plaques of erythema with or without scaling or pustules may be present. Conditions that can be associated with cicatricial alopecia include infections (e.g., syphilis, tuberculosis, acquired immunodeficiency syndrome, herpes zoster), autoimmune disease (discoid lupus erythematosus), sarcoidosis, scalp trauma (e.g., injuries, burns), and radiation therapy.

If the cause of the disorder is not readily apparent, a 4-mm punch biopsy of the scalp can be helpful. Frequent findings on biopsy include lymphocytic proliferation around the follicle, destroyed follicles, a thin and atrophic epidermis, and a densely sclerotic dermis.

Traumatic alopecia can be caused by cosmetic practices that damage hair follicles over time. Cosmetic alopecia has been linked to the use of brush rollers, curling irons, hair brushes with square or angular tips, and tight braiding of the hair. Chemicals used repetitively on the hair also can damage follicles. Examination of the scalp shows short broken hairs, folliculitis and, frequently, scarring.


Trichotillomania is the name given to habitual, compulsive plucking of hair from the scalp or other hair-bearing areas of the body. Over time, continual plucking of scalp hair will result in a hairless area, known as a bald spot. Long-term trichotillomania can result in permanent damage to scalp skin and to scarring alopecia. It is not known whether trichotillomania should be classified as a habit or as obsessive-compulsive behaviour. 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 person with trichotillomania often has guilt feelings about his or her “odd” behaviour and will attempt to conceal it.

Hair loss due to trichotillomania is typically patchy, as compulsive hair pullers tend to concentrate the pulling in selected areas. Hair loss due to this cause cannot be treated effectively until the psychological or emotional reasons for trichotillomania are effectively addressed.

The behaviour is frequently a response to a stressful situation. Women display this behaviour more often than men, and children more often than adults. Children are often aware that they are plucking their hair and may be amenable to behavioural interventions. When the behaviour persists into adulthood, patients may not acknowledge their actions.

Trichotillomania is often difficult to treat. A variety of pharmacologic agents, mostly antidepressants, have been tried with some success. A combination of pharmacologic and behavioural therapies also has been attempted.

Alopecia due to Infections & Infestations

Alopecia due to infections and infestations refers to hair loss caused by various infections or infestations that affect the scalp or hair follicles. These conditions can lead to hair loss either directly through damage to the hair follicles or indirectly as a result of the body’s immune response to the infection.

Some examples of infections and infestations that can cause alopecia include:

  1. Fungal Infections: Conditions like ringworm (tinea capitis) can cause hair loss. Fungal infections affect the scalp, leading to inflammation and hair breakage.
  2. Bacterial Infections: Certain bacterial infections, such as folliculitis (inflammation of hair follicles) or specific scalp infections, can cause hair loss if left untreated and if the inflammation damages the hair follicles.
  3. Parasitic Infestations: Infestations by parasites like head lice (pediculosis capitis) can cause scalp irritation, itching, and subsequent hair loss due to scratching or damage caused by the parasites themselves.

Treatment for alopecia due to infections and infestations typically involves addressing the underlying cause. This may include using antifungal medications for fungal infections, antibiotics for bacterial infections, or specific treatments to eliminate parasites. It’s important to consult a healthcare professional or dermatologist for an accurate diagnosis and appropriate treatment plan.

Diffuse Alopecia

Diffuse alopecia refers to a type of hair loss that occurs uniformly across the scalp, leading to a general thinning of hair rather than specific bald patches. Unlike focal alopecia, which presents as distinct bald spots, diffuse alopecia results in an overall reduction in hair density. It can be caused by various factors such as genetics, hormonal changes, stress, nutritional deficiencies, certain medications, or medical conditions like thyroid disorders or autoimmune diseases. Treatment typically involves addressing the underlying cause and may include medications, lifestyle changes, or topical treatments to manage the condition and encourage hair regrowth.

Alopecia due to Hair Shaft Abnormalities

Alopecia due to hair shaft abnormalities refers to hair loss resulting from structural defects or abnormalities in the hair shaft itself. These abnormalities can make the hair more prone to breakage, thinning, or loss. Hair shaft abnormalities can be genetic or acquired and may affect the hair’s strength, texture, and overall appearance.

Several conditions can lead to hair shaft abnormalities and subsequent alopecia:

  1. Monilethrix: This is a genetic condition where the hair shaft becomes beaded and fragile, leading to breakage and sparse hair growth.
  2. Trichorrhexis nodosa: Hair shafts develop weak points that lead to nodes or swelling along the hair shaft, making the hair more susceptible to breakage.
  3. Trichorrhexis invaginata (bamboo hair): This condition causes the hair to have a beaded appearance due to invaginations or nodules along the hair shaft. It’s commonly associated with conditions like Netherton syndrome.
  4. Pili torti: Hair shafts become twisted and brittle, leading to breakage and hair loss.
  5. Pili annulati: This condition causes the hair to have alternating light and dark bands due to air-filled cavities within the hair shaft. It may lead to hair fragility.

Treatment for alopecia resulting from hair shaft abnormalities often focuses on managing the condition and minimizing hair breakage. While some conditions may not have a cure, certain measures can help reduce damage and improve hair health. These may include gentle hair care practices, avoiding harsh chemicals or heat styling, using specialized hair products, and in some cases, treatments prescribed by a dermatologist to strengthen or protect the hair. Consulting with a healthcare professional or dermatologist is essential for proper diagnosis and guidance on managing these conditions.

Hereditary Alopecia

This type of alopecia involves hair loss that is influenced by genetic factors. It often progresses gradually over time and can be seen in various patterns, such as male or female pattern baldness. Male pattern baldness typically involves a receding hairline and thinning on the crown, while female pattern baldness may lead to overall thinning of the hair without a distinct receding hairline. These patterns of hair loss are often linked to genetic predispositions and hormonal influences. Treatments for hereditary alopecia can include medications like minoxidil or finasteride, hair transplants, or other procedures to manage hair loss.

Congenital Alopecia

This refers to hair loss that is present at birth or becomes apparent shortly after birth due to genetic conditions or abnormalities. Some congenital conditions, like congenital atrichia, cause complete absence of hair follicles, resulting in lifelong hairlessness. Others, such as ectodermal dysplasia, can affect not only hair growth but also the development of teeth and sweat glands. Treatment for congenital alopecia often involves managing associated symptoms and providing supportive care, as complete restoration of hair may not always be possible.