Children’s eyes are blue underneath, which may be caused by physiological reasons or pathological reasons such as trauma, heart disease, anemia and so on. 1. Physiological: the skin of children’s eyelids is relatively weak, with less subcutaneous fat and less pigmentation, which may reveal the color of the veins under the skin, manifesting as blueness under the eyes. 2. Trauma: when a child’s eyes are partially hit, it may lead to bruising under the eyelid skin, which is manifested as bluish color under the eyes. 3. Heart disease, anemia: heart disease, anemia and other diseases may lead to insufficient blood supply to the eyes, manifested as blue under the eyes. Specific causes need to go to the hospital for a comprehensive examination to clarify, it is recommended that parents take their children to the ophthalmology department of a regular hospital, to clarify the diagnosis, and follow the doctor’s instructions for treatment.