A little swelling of the penis in newborns may be caused by trauma, insect bite reaction, contact dermatitis and other diseases. 1. Trauma: If the newborn’s penis is hit, excessive pulling and so on, it may cause penile contusion, thus appearing penile edema. 2. Insect bite reaction: insect bite reaction occurs in exposed areas, newborns who do not wear diapers, resulting in the penis exposed, if the mosquito bites, will lead to localized redness, swelling, blisters, pimples and other symptoms, can be accompanied by itching. 3. Contact dermatitis: contact dermatitis is an inflammatory skin disease caused by skin contact with external substances, manifested as local erythema, swelling, pimples and other symptoms. If the child is allergic to the diaper and other materials, causing contact dermatitis, will cause the newborn penis a little swollen. There are many reasons for a swollen penis in newborns, so parents are advised to take their children to the doctor for a checkup to determine the cause.