The left side of the hair fell out a piece may be caused by external forces, but also may be mental factors, ringworm and other reasons, usually can be relieved by medication, hair transplantation treatment, life conditioning and other ways. 1. external force: if the hair loss caused by external pulling, usually do not need special treatment, usually within a short period of time the hair will grow, usually pay attention to protect the hair, avoid pulling vigorously. 2. Mental factors: the left side of the hair fell out of a piece may be stress, anxiety and other mental factors, it is recommended to pay attention to rest, maintain sufficient sleep, you can communicate, exercise and other relief of stress and anxiety. 3. Tinea capitis: If it is a dermatophyte infection, it may cause a piece of the left side of the hair to fall out. It is usually treated with medication under the guidance of a doctor, such as itraconazole, terbinafine and other medications orally, and combined with topical ketoconazole lotion, bifonazole lotion and so on. If the above methods cannot relieve the symptoms, and the hair loss seriously affects the aesthetic appearance, it is recommended to consult a doctor. The medication should be used according to the doctor’s instructions.