Eyebrows suddenly missing a piece may be baldness or alopecia areata folliculitis caused. 1. Patchy baldness: It is currently believed that patchy baldness is related to autoimmune, emotional stress, endocrine or genetic factors, and mental factors are more important triggering factors. The patient manifests sudden, clear-cut hair loss, usually without other uncomfortable symptoms, if the scope of hair loss is large, it is necessary to seek medical treatment. 2. Alopecia Areata Folliculitis: Alopecia Areata Folliculitis is easy to destroy the hair follicles, resulting in the hair inside the follicles falling out and unable to grow, so the symptoms of hair loss may occur. If there is a sudden lack of eyebrow hair, it is recommended that the patient go to the hospital in time to do a checkup to clarify the cause of the disease and then do targeted treatment.