Three-month-old babies with smelly ears may have eczema of the external ear canal, otitis media, or excessive cerumen. 1. Eczema of the external auditory canal: it is usually caused by milk, tears, bath water, etc. entering the external auditory canal and stimulating the eczema, which manifests itself as itching, and the baby shakes his head and pats his ears to stop the itching. 2. Otitis media: can be caused by colds, or bacterial infections, bacteria and viruses can invade the middle ear and cause infection. Symptoms include earache, hearing loss, running water in the ear canal, and a foul odor when pus develops. 3. Excessive cerumen: Excessive cerumen in the ear canal, which has existed for too long, can lead to odor in the ear canal, which can be removed in time. There may be other reasons why a three-month-old baby’s ears smell bad, so it is recommended that you go to the hospital in time for a complete examination to determine the cause of the problem and then give targeted treatment or therapy.