Hair Shaft Defects

There are numerous conditions in which physical damage to the hair fiber results in hair loss. Sometimes this damage occurs due to improper hair formation by the hair follicles. These conditions are often caused by genetic defects. Additionally, there are conditions where physical hair fiber damage is due to environmental factors, most commonly poor or inappropriate hair care practices. While hair loss due to physical hair defects is rare compared to other causes of alopecia, the most common ones are listed below.

Loose anagen syndrome

Loose anagen syndrome, also known as loose hair syndrome, involves precisely what the name suggests: growing hair that is “loose” and easily pulled out of the hair follicle. This syndrome is usually first diagnosed in young children, particularly in girls. Affected individuals have hair that seems to never grow, requiring infrequent haircuts, and their scalp hair is often thin, especially at the back of the head. The hair’s loose and easily pulled-out nature explains why the back of the head is most affected. Repeated friction of the head against a pillow at night can lead to hair loss at the back of the head, while the front of the scalp is less affected due to less pillow contact. The remaining hair usually doesn’t grow very long and can be unruly and challenging to comb and style. Loose anagen syndrome is most likely to affect blond-haired children aged 2 to 5 years, but it can also manifest later in life. The syndrome tends to improve with age in children, but its onset in older individuals indicates that hair loss will likely persist. The precise cause of the loose hair is not definitively known, but individuals with loose anagen syndrome typically have improperly formed root sheaths that surround and protect hair shafts in the skin. Due to the incomplete formation of root sheaths, adhesion between the hair shaft and the root sheath is lacking, resulting in poorly anchored hair fibers in the hair follicle. While genetic factors might contribute to this syndrome, isolated cases have been reported without a family history. Unfortunately, there are no known effective treatments for loose anagen syndrome.

Traction alopecia and trichotillomania

Traction alopecia and trichotillomania both lead to hair loss through similar mechanical actions. In both cases, hair is plucked from the skin, causing either clear bald patches or diffuse, thin hair. Traction alopecia can result from factors like tight hat bands, tight ponytails, cornrow hair styles, and any other practices that exert tension on hair roots. Prolonged traction alopecia, where the same hair is repeatedly pulled out, can lead to permanent hair follicle damage and permanent hair loss.

Trichotillomania is a condition in which affected individuals compulsively pull out their own hair. While scalp hair is often targeted, individuals may focus on eyelashes, eyebrows, pubic hair, or any hair-bearing area. Debate exists as to whether trichotillomania is a habit akin to nail biting or a more complex psychological issue. Regardless, individuals with this condition are often unaware that they are engaging in hair pulling, and when made aware, they struggle to cease the behavior. Some individuals who pull out their hair may also engage in hair consumption, known as “trichophagia.” This dangerous behavior requires urgent treatment, as hair is indigestible and can accumulate to form hair balls in the stomach, leading to severe ulceration and even death. Treating trichotillomania is challenging, with therapists potentially offering more assistance than dermatologists.


Monilethrix causes hair fibers to resemble strings of beads. Nodes and constrictions along the hair fiber create an undulating edge. This beaded structure weakens the hair, resulting in diffuse hair loss for those with monilethrix. The condition often leads to hair loss at the back of the scalp and neck while sparing the front of the head. Monilethrix can also affect hair on other parts of the body. Under a microscope, hair fibers affected by monilethrix exhibit lost cuticle covering over the nodes, whereas the constrictions maintain their cuticle. Once the brittle hair is exposed above the skin, it breaks easily, and the fibers rarely grow very long. Breakage usually occurs at the weak constriction points along the fiber. While monilethrix is more common in childhood, young adults can also develop it. It is genetically inherited and can run in families, though varying degrees of severity may affect different family members. The condition’s severity may fluctuate with seasons, often worsening in winter and improving in summer. While monilethrix might spontaneously improve, many individuals live with the condition throughout their lives.

Overprocessing, cuticle stripping, and bubble hair

Overprocessing the hair is the leading cause of physical hair damage. Chemical treatments like perming, straightening, bleaching, and dyeing involve harsh chemicals that significantly affect hair fiber integrity. Frequent or improper use of these methods can cause irreversible damage to hair fibers, weakening them and making them prone to breakage.

The hair cuticle, composed of dead and highly keratinized cells, acts as a protective outer sleeve for the hair fiber. These scales overlap like fish scales along the length of the hair. Excessive processing can damage and “flake up” these overlapping scales. For chemical treatments like perms, straighteners, bleaches, and dyes to work, the cuticle must be opened, allowing other chemicals to access the hair cortex to rearrange chemical bonds or alter pigmentation. Prolonged application of these chemicals, high concentrations, or frequent exposure can irreversibly damage or completely strip away the cuticle. This exposes the softer cortex to the environment, resulting in dull, dry, and frizzy hair. Factors like shampoo chemicals, water, air pollution, and UV light exposure can further weaken the hair cortex. Eventually, the hair may become so weak that it splits or breaks off completely. Severe chemical processing can weaken the hair fiber from the root, leading to breakage at the skin surface and causing diffuse “alopecia.”

Apart from chemical-induced damage, physical processes can also harm hair. Aggressive brushing, backcombing, and other grooming methods that stress the hair can lead to cuticle flaking and stripping. Misuse of hair dryers can also cause significant damage. When you wash your hair, water can penetrate the cuticle and reach the cortex. Using high heat to dry your hair heats the water, causing it to expand inside the hair and create spaces within the fiber. Severe cases can result in the formation of bubbles within the hair, a condition aptly named “bubble hair.” These bubbles weaken the hair, making it prone to breakage. Combining damaging physical processes with harmful chemical treatments exacerbates the problem.

Treating hair damaged by overprocessing is challenging. The best approach involves trimming damaged hair, avoiding further chemical processing, treating hair gently, and waiting for new, undamaged hair to grow in. While cosmetic treatments can temporarily “repair” damaged hair, they require frequent reapplication and are never as effective as the original, undamaged hair.

Trichorrhexis Nodosa

Trichorrhexis nodosa, also known as trichonodosis, is one of the most common hair shaft defects encountered by dermatologists. It presents as localized defects along the hair fiber, where the hair appears normal under the microscope except for isolated areas showing swelling or fraying. These defects develop in regions lacking cuticle.

Causes of trichorrhexis nodosa can be congenital or acquired. Congenital trichorrhexis nodosa is rare but may result from naturally weak hair with improperly formed cuticles. This form is usually hereditary, occurring within families, and starts at a very young age. Abnormal hair fiber production characterized by irregular and brittle hair can also arise from metabolic disorders involving abnormal urea synthesis, copper or zinc metabolism, or deficient cysteine or sulfur incorporation into hair (trichothiodystrophy). Acquired trichorrhexis nodosa is more common and results from excessive hair manipulation and overprocessing. Excessive brushing, hairstyles that strain hair, frequent washing, dyeing, and perming can disrupt the cuticle in specific areas along the hair shaft. It is particularly seen in individuals who overuse hot combs or permanent waves. If the cuticle is removed from hair fiber, the hair cortex rapidly breaks down.

Treatment varies based on the suspected cause of the focal defects. When abnormal hair production is suspected, treatment targets the hair follicle to strengthen hair fiber. If excessive grooming is the cause, the primary action is to minimize hair manipulation. Individuals are advised to avoid brushes, limit chemical styling, and use mild shampoos.