The darkening of the lower eyelid of a child may be caused by bad habits, trauma, conjunctivitis, etc. It can be treated by improving living habits, alternating hot and cold compresses, and using antibiotic drugs. 1. Bad living habits: If children stay up late for a long time, look at the cell phone, overwork, etc., the phenomenon of darkening of the lower eyelids may occur. It can be relieved by improving lifestyle habits, such as going to bed early and waking up early, avoiding staying up late. 2. Trauma: If a child suffers a traumatic injury, it may lead to bruising under the eyelids and darkening of the lower eyelids. Cold compresses can be applied within 24 hours of the injury, and hot compresses can be applied for more than 24 hours to relieve the symptoms. 3. Conjunctivitis: Children with conjunctivitis may develop darkening of the lower eyelid due to poor circulation. If it is caused by bacterial infection, it can usually be treated by using antibiotic drugs, such as levofloxacin hydrochloride eye drops, ciprofloxacin hydrochloride eye drops, etc., and it is forbidden for those who are allergic to the ingredients of the drugs. If the darkening of the lower eyelid persists and cannot be relieved by rest or is accompanied by other eye discomfort, it is recommended to consult a doctor for a detailed examination and follow the doctor’s instructions. All medications should be used under the guidance of a doctor, and should not be used privately to avoid aggravating the condition.