The forehead bag may be caused by trauma, also may be caused by mosquito bites, folliculitis, epidermal cysts, dermatitis, tumors and other diseases, such as symptom aggravation, should promptly seek medical attention, clear cause treatment. 1, trauma: forehead by sharp objects hit or bump may cause local hematoma, thus the bag. It is recommended to go to the hospital to check whether the damage is serious, and then according to the situation; 2, mosquito bites: when the mosquito bites the forehead skin, mosquito venom will lead to skin allergy and inflammatory reaction, forehead red bag, and accompanied by certain itching symptoms, usually about 2-7 will naturally subside; 3, folliculitis: when the bacterial pathogens infect the forehead hair follicles, thus triggering inflammation, resulting in the forehead to appear on the hair follicle as the center of the red mass, sometimes the top will also appear white pustules, may have itching or tenderness symptoms; 4, epidermal cysts: due to a variety of reasons resulting in epithelial cells implanted in the subcutaneous growth and become, more dome-shaped raised skin swelling, the surface can be seen in the sebaceous gland openings of small black spots, the sac with sebum and epidermal keratinized material gathered, mostly seen in the sebaceous gland distribution dense areas, such as the head and face and back; 5. Danemia: mostly inflammation caused by Streptococcus b haemolyticus infection, typically marked by edematous erythema with clear borders, bright surface tension and rapid expansion around. When the facial forehead is infected by streptococcus to the superficial lymphatic vessels of the dermis, it will lead to a long forehead bag with pressure pain and elevated skin temperature; 6, tumor: head tumors such as lipoma, fibroma, etc. will also make the forehead bag. Most of these tumors are benign and do not require too much worry. It is recommended to go to the hospital to follow the doctor’s advice for treatment and regular re-examination.