Forehead inexplicably swollen a bag, consider the following several possibilities: 1, dengue: can appear clearly defined edematous erythema, slightly arched over the surface of the skin, accompanied by symptoms of elevated skin temperature, pressure pain. In clinical treatment, you can apply penicillin sodium injection static, external application of compound polymyxin B ointment, this disease is due to hemolytic streptococcal infection. 2, insect bite dermatitis: may be due to mosquito bites after the appearance of the rash, accompanied by a certain sense of itching. Treatment can be oral chlorpheniramine maleate tablets, 3 times / day, 4 mg / times, external zinc oxide boric acid ointment for application of treatment. 3, boils: mainly due to bacterial infection caused by the touch of pain, can be oral amoxicillin capsules, external fusidic acid cream application of treatment.