Hair oil alone cannot determine whether it is kidney yang deficiency or kidney yin deficiency, and it needs to be analyzed according to the patient’s other clinical symptoms. For patients with kidney yang deficiency, clinical manifestations often include cold pain in the waist and knees, long and clear urination, and cold limbs (fear of cold, cold limbs), etc. For patients with kidney yin deficiency, clinical manifestations often include soreness in the waist and knees (a feeling of soreness and weakness in the waist and knees), and heartburn and heat (heat in the hearts of the hands and feet, and self-consciousness of the heart and chest heat). For hair oil, it may be due to the prevalence of dampness and heat in the body or vegetarian diet favoring spicy and greasy food, etc. It is generally not related to kidney yin deficiency or kidney yang deficiency. However, the exact cause needs to be decided according to the patient’s other clinical symptoms. If the condition of hair oil is more serious, it is recommended to consult a doctor in time.