I have examined many singers who have chronic sinusitis.
Sinusitis is inflammation of the sinuses, which is in any of the hollow areas of the skull around the nose. Sinusitis may be caused by anything that interferes with air flow into the sinuses and the drainage of mucous out of the sinuses, such as infection, allergies, air pollution, or structural problems in the nose. The most common symptoms are thick nasal mucus, a plugged nose/congestion, difficulty breathing, and/or facial pain. The combination of swollen nasal membranes and excess mucus make it difficult to breathe normally through the nose. This blockage can affect and alternate between one or both sides of the nose.
The most recent case I observed was a young man who started having the chronic sinusitis when he as kid. His paranasal sinuses (moreover the maxillary sinus) were constantly filled with mucus and pus. Over the years he had tried many antibiotics as well as just ignoring the problem hoping it would resolve itself. I examined him physically, then factored in his history and discussed his vocal expectations. He is generally good at singing slow tempo ballads, but not fast tempo music like pop. I recorded his voice, which sounded a little boxy and soft. His paranasal sinuses were filled with mucus and pus at the time of the first recording.
Next, I recommended him to take a Chinese herbal remedy to treat the sinusitis. I recorded his voice again after a few weeks of the treatment. After reviewing the recording, I determined that his voice indeed sounded clearer and brighter than when we first recorded before. I then let the young man hear the two recordings. When comparing the two recordings of his voice, he also agreed that the voice after the treatment obviously sounded better than the other. Following his treatment the young man was able to breath easier through a clear nasal passage. Overcoming the chronic sinusitis gave him the physical ability to vocalize normally, which raised his confidence, and he reached his goal of being good at singing fast tempo music.
The paranasal sinuses are normally filled with the air, but in the case of sinusitis the paranasal sinuses are filled with pus and/or mucus.
The paranasal sinuses in the nasal cavity create resonance when singing, it always has to be clear and hollow.
If there is foreign matter in the paranasal sinuses, or an abundance of mucus/pus, that will obstruct the voice’s resonance and make vocalization sound bad.
Please seek treatment for chronic sinusitis, if you have it.