Redness and warmth in one ear can be caused by a variety of reasons, including poor sleeping posture, mosquito bites, inflammatory reactions, etc. 1. Bad sleeping position: If the child always sleeps with his head on one side, the ear is compressed, which may lead to poor local blood circulation and cause redness and heat in the ear. 2. Mosquito bites: If the child shows itching, the ear may have been bitten by mosquitoes, resulting in localized swelling of the skin and mucous membrane redness and heat. 3. Inflammatory response: If the patient has symptoms of elevated body temperature, it may be due to the invasion of pathogens causing an inflammatory response in the body. At the same time, local inflammation folliculitis and other inflammatory stimuli can also cause redness and swelling of the skin mucosa, redness and fever. If the symptoms have not been relieved, it is recommended to consult a doctor to clarify the diagnosis.