Swelling of the baby’s upper lip is mainly caused by diseases, and common causes include allergies, trauma, mosquito bites, oral ulcers and so on. When the baby is exposed to some allergens such as fish and shrimp, milk, dust, external environmental stimuli leading to allergies, can cause the child to develop angioneurotic edema. Affected children often have symptoms such as swelling and thickening of the lips and a mild burning sensation. Allergens should be kept away in time. In the course of daily activities, the baby’s lips unintentionally bumped, bruised localized may also appear edema. Summer mosquitoes, venomous insects more, if the precautions are not enough, the baby may be mosquito bites. When the mosquito bite after the mosquito secretion into the skin to cause a reaction, thus showing the phenomenon of localized swelling. Vitamin deficiencies in the body as well as a decrease in autoimmunity can also trigger swelling of the lips when mouth ulcers are caused. When your baby is not feeling well, you should go to the hospital immediately.