A hard bag on the forehead may be caused by trauma, folliculitis, fibroma and other diseases, the patient should consult a doctor in time to clarify the cause of the disease after treatment. 1. If the patient has had a forehead collision before the forehead grows a hard bag, then we should consider that it is caused by trauma, and we should go to the regular hospital in time. 2. Folliculitis: frontal hair follicles can be infected by bacteria, fungal infection can also cause a hard bag on the forehead, the patient may also have local redness, swelling, pain, can be used locally fusidic acid, bifonazole and other drugs for treatment. 3. Fibroma: forehead long a hard bag may also be caused by fibroma, which is formed by excessive proliferation of subcutaneous fibrous tissue, generally benign, can be surgically removed. A hard bag on the forehead may also be caused by other causes, it is recommended to consult the dermatology department of the hospital, the above drugs and treatments should be carried out under the guidance of a doctor.