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There are a multitude of conditions where physical damage to the hair fiber results in hair loss. Sometimes this damage to the hair fiber is due to the hair being improperly formed by the hair follicles. These conditions are usually determined by genetic defects. There are also conditions where physical damage of the hair fiber is caused by something environmental, most often poor or inappropriate hair care. Hair loss as a result of physical hair defects are rare compared to other causes of alopecia, but some common ones are listed below.
Loose anagen syndrome . Loose anagen syndrome or loose hair syndrome involves exactly what the name suggests, growing hair that is "loose" and easily pulled out of the hair follicle. Loose anagen syndrome is most often first diagnosed in young children, more so in girls than boys. Their hair never seems to grow, they rarely ever need a hair cut, and the scalp hair is usually thin, especially at the back of the scalp. That the hair is loose and easily pulled out helps explain why the back of the head is most affected. The repeated rubbing of a person's head on a pillow at night pulls out more of the hair on the back of the head, whereas the front of the scalp has less contact with the pillow and so the hair is more likely to remain in place. The remaining hair usually does not grow very long and it can be unruly and difficult to comb and style. Blond haired children age 2 to 5 years are most likely to be affected but loose anagen syndrome can appear later in life as well. The syndrome improves with age of its own accord in children, but development in older individuals indicates the hair loss will be more persistent. Why the hair is loose is not known for sure, but the root sheaths that normally surround and protect the hair shaft in the skin are not produced properly in people with loose anagen syndrome. It seems that because the root sheaths are not fully formed there is a lack of adhesion between the hair shaft and the root sheath and the hair fiber is poorly anchored in the hair follicle. There may be a genetic problem behind loose anagen syndrome and the condition can run in families, but there are also many isolated case reports with no family history. There are no known effective treatments for loose anagen syndrome.
Traction alopecia and trichotillomania . In terms of the mechanical action that causes hair loss, traction alopecia and trichotillomania are exactly the same. The hair is plucked out of the skin leaving clear bald patches or diffuse, thin hair. With traction alopecia the cause may involve things like tight hat bands, pulling the hair into a tight pony tail, cornrow hair styles, and anything else that pulls on the roots of the hair. If traction alopecia continues for a long time and the same hair is repeatedly pulled out then the hair follicles in the skin can become so damaged that they stop growing hair permanently.
Trichotillomania is a condition in which the affected individual plucks out their own hair. Often the hair on the scalp is plucked to leave bald patches, but the individual may focus on the eyelashes, eyebrows, pubic hair, or any other hair bearing region. There is much argument about whether trichotillomania is a habit like nail biting, or a more psychological problem. Either way, affected individuals are usually not aware that they are plucking their hair and when they are made aware of it they often find it very hard to stop. Some individuals who pluck their hair also then eat it, a condition called "trichophagia". This is a very dangerous condition that needs to be treated with some urgency. Hair is not digestable in the stomach, it can build up into a hair ball. This can severely irritate the stomach lining leading to severe ulceration. It is possible to die from trichophagia. Treating trichotillomania is difficult; therapists can probably help more than dermatologists.
Monilethrix . The condition monilethrix makes hair fiber look like a string of beads. Along the length of a hair fiber there are nodes and constrictions making the edge of the fiber undulate. This hair beading weakens the fiber and people with monilethrix have diffuse hair loss. Most frequently the hair loss is at the back of the scalp and neck and can leave the front of the head relatively unaffected. Monilethrix can also affect hair in other regions of the body. Under a microscope, the hair fibers can be seen to have lost their cuticle covering over the nodes while the constrictions keep their cuticle. The brittle hair easily breaks once it is exposed above the skin and the fibers rarely grow very long as a result. Breakage occurs in the weak constriction points along the fiber. Monilethrix most often occurs in childhood but young adults can also develop it. It is a genetically inherited disease and can run in families, although different family members may be affected to different degrees of severity. The severity of monilethrix can also change with the seasons. It is often worse in winter and improves in summer. Monilethrix may spontaneously improve, although many people have monilethrix for their entire lives.
Overprocessing, cuticle stripping, and bubble hair . Overprocessing the hair is the most common cause of physical hair damage by far. Perming, straightening, bleaching, and dyeing the hair all involve quite harsh chemicals that can significantly affect the integrity of hair fiber. Using these cosmetic approaches too frequently or inappropriately can lead to irreversible damage to the hair fiber. The more hair fiber is damaged by these processes the weaker it will be and the more likely it will break off.
The hair cuticle is a very strong outer sleeve of dead and highly keratinized cells that overlap each other like fish scales along the length of the hair fiber. The cuticle helps protect the softer inner cortex structure of the hair fiber from damage. The overlapping scales of the cuticle may become damaged and "flake up" if they are exposed to too much processing. For perms, straighteners, bleaches, and dyes to work the cuticle has to be opened up so that other chemicals can get to the hair cortex and either rearrange the chemical bonds in the hair structure, as occurs with perms and straighteners, or to remove or add hair pigment, as occurs with bleaching and dyeing. If the chemicals to open the cuticle are applied for too long, in an unsuitably high concentration, or too frequently the cuticle may be irreversibly damaged and even stripped away completely. When this happens the softer cortex is exposed to the environment. The cortex does not have the same properties of the cuticle, it has a rough surface, so at this stage the hair can look dull, "dry" and frizzy. Chemicals in shampoos, in the water, in air pollution, combined with UV light exposure can all contribute to further damage and weakening of the hair cortex. Eventually, the hair may become so weak that it splits or breaks off completely. More usually, this splitting and breakage occurs to old hair, that is, towards the end of the hair fiber. However, if the chemical processing is very severe, it alone can do so much damage to the hair fiber that the fiber at the root is severely weakened. If this happens, the hair may beak off at the skin surface. The result is a diffuse "alopecia".
As well as chemical induced damage, physical processes can also damage the hair. Aggressive brushing, back combing, and other grooming techniques that put a lot of physical stress on the hair fiber can cause the cuticle to flake and strip away. Inappropriate use of the hair dryer can cause a lot of damage. When you wash your hair, some water gets under the cuticle and into the cortex. If you dry your hair with a high heat you heat up the water. This makes the water expand inside the hair and this literally pushes outwards to leave spaces in the hair fiber. In severe cases the hair develops little bubbles inside, a condition appropriately called "bubble hair". These bubbles make the hair much weaker and likely to break off. If damaging physical processes are combined with damaging chemical processes then the problem is compounded.
Physical damage to the hair through overprocessing is difficult to treat. The best approach is to cut off as much damaged hair as possible, avoid further chemical processing, be gentle with your hair and wait for new, undamaged hair to grow in. While there are cosmetic treatments to help "glue" damaged hair back together, they only work for a short time and have to be reapplied regularly. The end result is never as good as the original, undamaged hair.
Trichorrhexis nodosa . One of the most common hair shaft defects a dermatologist encounters is trichorrhexis nodosa (also called trichonodosis). Trichorrhexis nodosa is a focal defect in the hair fiber. When observed under the microscope most of a hair shaft looks entirely normal. However, in isolated spots along the length of a fiber swelling and/or fraying can be seen. These focal defects develop where there is an absence of cuticle.
Causes of trichorrhexis nodosa can be congenital or acquired. Congenital trichorrhexis nodosa is very rare, but some people have naturally weak hair where the cuticle is not properly produced. Congenital trichorrhexis nodosa is usually hereditary, it runs in families, and it first develops at a very young age. Abnormal production of hair fiber that is irregular and brittle can also occur in metabolic disorders such as those that involve abnormal urea synthesis, abnormal copper or zinc metabolism, or defective cysteine or sulfur incorporation into hair fiber (trichothiodystrophy). Acquired trichorrhexis nodosa is much more common and develops as a result of excessive hair manipulation and over-processing. Too much brushing, hairstyles that put constant stress on the hair, excessive washing, dying, and perming may disrupt the cuticle in focal areas along a hair shaft. Trichorrhexis nodosa is particularly seen in people who overuse hot combs or permanent waves to style their hair. Once the cuticle is removed from hair fiber then the hair cortex swiftly breaks down.
Treatment depends on the considered cause of the focal defects. If the hair production is believed to be abnormal then treatment will focus on the hair follicle and improving the strength of hair fiber. Where the defect is the result of excessive grooming the obvious action is to reduce the amount of hair manipulation. People are encouraged to stop using brushes, avoid hair styling that involves chemicals and use only very mild shampoos.