Breakage of the hair shaft as a result of acquired structural abnormalities in the hair brought on by stressful hair-care procedures can also result in traumatizing alopecia. Acquired trichorrhexis nodosa is the most prevalent defect; it manifests at any age as short, brittle hairs that break readily. The hairs’ distal ends are frayed, giving them a broomstick-like appearance under the microscope . Under a microscope, certain hairs may contain nodules that seem like two broomsticks stuck together. The most prevalent causes of acquired trichorrhexis nodosa in black people are injuries sustained when combing tightly curled hair or overusing hot combs, hair dryers, straighteners, or other chemicals. When the harm source is removed, normal hair growth resumes. This condition is self-limiting.
Alopecia can also result from other intentional or unintentional physical, thermal, or chemical injuries to the scalp and hair shaft. Child maltreatment and pressure necrosis of the skin are two examples.