Earwax is also known as cerumen, and its smell is not obvious under normal circumstances. If it is accompanied by a foul smell, it is mainly seen for the following reasons: First, water or some dirty things in the ear canal can lead to local swelling of the earwax, resulting in decay and deterioration of the earwax components and thus a foul smell. Second, the patient has chronic purulent otitis media with long-term pus in the ear canal, or eczema in the external ear canal with frequent flowing water in the ear canal, or chronic otitis externa with some inflammatory secretions in the ear canal, and the above-mentioned things mixed with the earwax can cause the earwax to have a foul odor. If the earwax has a foul odor, you usually need to go to an outpatient clinic for cleaning to avoid causing further aggravation of the infection. If the patient has otitis media, he or she will also need to have a CT scan of the middle ear and other appropriate tests.