A large hard bump between the eyebrows may be associated with acne, boils and epidermal cysts. 1. Acne: Its causes may be related to endocrine, infections and abnormal keratinization of sebaceous glands, etc. Patients may have pimples, acne, pustules and nodules or cysts, etc., which are commonly found on the face. 2. Boils: usually manifested as one or more painful nodules, commonly found on the face and buttocks, etc. Its cause is mostly related to Staphylococcus aureus infection. 3. Epidermal cysts: their causes may be related to abnormal skin development, trauma and other factors, the patient’s skin will appear dome-shaped raised skin swelling, mostly in the head and face, upper trunk and other places. There are many reasons that lead to a large hard bag between the eyebrows, and it is recommended that patients seek medical examination to clarify the cause of the disease.