Common causes of hard bumps on the forehead that look like bone bumps include epidermal cysts, bone tumors, boils, and trauma. 1. Epidermoid cysts: some epidermoid cysts can be primary cysts of unknown cause, but some epidermoid cysts can be caused by trauma, friction, surgery and other factors leading to the destruction of follicle structure, epithelial cells implanted in the dermis growth. They are characterized by hemispherical cystic swellings that are elevated on the surface of the skin, have a smooth surface, and feel tough and tense to the touch. 2. Bone tumor: the etiology of this disease is not clear, may be related to genes, endocrine factors, viral infections and other factors. It is manifested by the appearance of subperiosteal or superficial tumors, palpable bone swelling and deformation, smooth or uneven surface and other symptoms. 3. Boils: Boils are mainly caused by acute bacterial infection of hair follicles and their sebaceous glands. It is characterized by hardening of the hair follicle, redness and swelling around it, pain, and the formation of small yellowish-white pus plugs. 4. Trauma: When the forehead is traumatized, it can cause local tissue bleeding, resulting in hematoma under the skin, and in serious cases, fractures may occur, which may be manifested as a hard bag on the forehead that looks like a bone protruding. It is recommended that patients go to the regular hospital dermatology department, follow the doctor’s instructions to clarify the diagnosis, active treatment, to avoid delaying the condition.