Swelling under the eyes of children may be related to physiological factors, or it may be caused by trauma, insect bite dermatitis, blepharitis, foreign body in the eye and so on. 1. Physiological factors: it may be due to drinking too much water at night before going to bed, and the body’s metabolism is slow after going to bed, which may cause swelling under the eyes. 2. Trauma: when you play, your eyes are hit by external force, under the effect of gravity, it may cause swelling under the eyes, which may be accompanied by localized bruising, pain and other manifestations. 3. Insect bite dermatitis: often appear in the hot summer, due to more mosquitoes, if the lower part of the eye is inadvertently bitten by mosquitoes, it is easy to induce insect bite dermatitis, under the stimulation of inflammation, it may cause swelling under the eye, but also accompanied by obvious itching, pain and other symptoms. 4. Blepharitis: due to unhygienic eye use and frequent rubbing of the eyes with dirty hands, blepharitis is easily induced, which may cause red, painful lumps under the eyes, resulting in swelling under the eyes, which may be accompanied by congestion and tearing of the eyes. 5. Foreign body in the eye: If a child gets a foreign body in the eye and fails to remove it for a long time due to an abnormality, it may cause swelling under the eye. Swelling under the eyes of children may also be caused by other reasons, if the symptoms are serious, or there are other symptoms of discomfort, you should consult a doctor as soon as possible, to clarify the cause, and then follow the doctor’s instructions for treatment.