Children’s lower lip suddenly swollen may be due to trauma, mosquito bites or allergies and other reasons. 1. Trauma: when the child’s lower lip is hit by external forces, there will be localized swelling, accompanied by pain, sometimes accompanied by localized bleeding, especially next to the teeth of the part of the situation will appear broken. 2. Mosquito bites: in the summer time to pay attention to mosquito bites caused by mosquito bites, children’s lower lip after being mosquito bites can also cause swelling, can be accompanied by itching and other symptoms. 3. Allergy: may be caused by allergies, mostly because of the lower lip localized contact with some kind of allergy can lead to the material, so that the whole lower lip is swollen. Children’s lower lip suddenly swollen may also have other reasons, it is recommended to go to the hospital in a timely manner, improve the examination to clarify the cause of the disease, give targeted treatment or treatment.