Loss of eyebrow hair may be considered to be the precursor of hypothyroidism, systemic infectious diseases (leprosy, syphilis, etc.), pemphigus vulgaris, local inflammatory diseases (e.g., folliculitis, neurodermatitis, seborrheic dermatitis); the occasional loss of a few eyebrow hairs belongs to the physiological phenomenon. 1. Hypothyroidism: caused by autoimmune diseases, medications and other reasons, the thyroid gland produces too little hormone or thyroid hormone utilization disorders can occur hair loss and other symptoms, such diseases caused by hair loss for the whole body, in addition to eyebrow hair loss, there are also phenomena such as hair thinning; and even symptoms of generalized baldness. 2. Systemic infectious diseases: the systemic sexually transmitted disease syphilis caused by syphilis spirochete (TP) infection will have the performance of patchy hair loss, commonly found in patients with second-stage syphilis; leprosy caused by Mycobacterium leprae infection will have patchy hair loss, often found in patients with severe leprosy, and in the eyebrow area, it usually manifests as hair loss of the outer 1/3 of the eyebrow. 3. Patchy baldness: Patchy baldness caused by autoimmune deficiencies, heredity, neuropsychiatric factors, etc. can show sudden and limited patchy hair loss, and can also have the manifestation of eyebrow hair loss. 4. Local inflammation: if you suffer from severe folliculitis, seborrheic dermatitis, neurodermatitis, etc., it will lead to serious damage to the hair follicles, or repeated scratching, etc. can also appear to fall out of hair (such as eyebrow hair) performance. In addition, patients who are chronically malnourished, overworked, severely anemic, or in the late stages of cancer may also experience eyebrow hair loss. It is recommended that patients with sudden and massive loss of eyebrow hair should go to a regular hospital in time to clarify the cause of the disease and follow the doctor’s instructions for treatment.