The causes of redness under a child’s eyes include allergies, mosquito bites, blepharitis and so on. 1. Eye allergy: the child is allergic to certain substances in the environment, such as pollen, dust, etc., which stimulates the body to produce an allergic mutation reaction, resulting in the eyes of the local loose tissue congestion and edema. 2. Mosquito bites: the toxic substances secreted by mosquitoes after biting the lower part of the eye stimulate the body to produce an inflammatory reaction, causing congestion, edema and itching under the eye. 3. Blepharitis: mainly caused by staphylococcal infection. In addition, conjunctivitis and other diseases can also cause redness under the eyes. If the above symptoms are not relieved, or accompanied by other symptoms, you should go to the hospital in a timely manner to clarify the cause and provide targeted treatment.