One swollen eye can be caused by mosquito bites, eye trauma, eye allergies, blepharitis and other reasons. 1. Mosquito bites: often appear in the summer and fall seasons, due to more mosquitoes, if the baby’s one eye is mosquito bites, due to the baby’s delicate skin, easy to cause one eye swollen, may also be accompanied by eye itching, pain and other symptoms. 2. Eye trauma: baby in the usual play process, if accidentally one eye is traumatized, it may cause an eye swelling, may also be accompanied by local pain, bruising and other manifestations. 3. Eye allergy: if the baby himself belongs to the allergic body, after the hand contact with some allergic substances, go to rub the eye, may cause eye allergy, may lead to one eye swelling, may also be accompanied by eye itching, redness and other manifestations. 4. Blepharitis: This is usually caused by the baby’s frequent rubbing of the eyes with dirty hands, due to the presence of inflammatory infections at the eyelid margins, which may cause swelling of the eyes under the stimulating effect of inflammation. If one eye has blepharitis, it can lead to swelling in one eye. One swollen eye can be caused by other reasons. If the symptoms are serious or accompanied by other discomforts, it is recommended to go to the hospital as soon as possible to clarify the cause of the swelling, and then carry out targeted treatment.