One year old baby legs suddenly long bag, should be treated according to the cause, if it is folliculitis can be used externally antibiotic ointment; insect bite dermatitis, etc. can use antihistamines, and glucocorticoid drugs. 1. Folliculitis: the skin follicles on the legs are infected by bacteria and other microorganisms caused by the inflammatory reaction, which can lead to a one-year-old baby legs suddenly long bag, bacterial infection caused by the person can be used externally mupirocin ointment, erythromycin ointment and other antibiotic medication. 2. insect bite dermatitis: the baby was bitten by insects after the occurrence of allergic reactions can also lead to long bags, you can follow the doctor’s instructions to take cetirizine hydrochloride drops and other antihistamines; can also be used externally hydrocortisone ointment and other glucocorticosteroid medication. One year old baby legs suddenly long bag, there may be other reasons, need to go to the hospital in time to check, follow the doctor’s advice treatment.