Redness in one eye of a child may be caused by visual fatigue, foreign body irritation, eye trauma, eye allergy, conjunctivitis and so on. 1. Visual fatigue: if children watch TV for a long time, look at the phone, rest is not good, it may lead to visual fatigue, resulting in eye capillary congestion, causing red eyes, accompanied by tears, dry eyes and other discomforts, but mostly in both eyes. 2. Foreign body irritation: when a child’s eye into the dust particles, small insects, shampoo, may form a conjunctival stimulation, resulting in conjunctival congestion, resulting in redness of the eyes, may also be accompanied by a foreign body sensation in the eye performance. 3. Eye trauma: If a child accidentally bumps and injures one eye while playing, causing contusion of the eye tissue, the redness of the eye may also appear, accompanied by eye swelling, pain, bleeding and other symptoms. 4. Eye inflammation: When a child’s eye is exposed to pollen, dust and other allergens, it may cause an allergic reaction in the eye, and under the stimulation of inflammation, the patient’s conjunctiva becomes congested, and the symptom of red eyes may appear. If the child often rubs the eye with dirty hands, it may lead to infection of the eye surface tissues, and the child may also have red eyes. It is recommended that children with significant redness in the eyes seek prompt medical attention to evaluate the condition and to follow the doctor’s instructions.