My cousin has had nodular acne for at least 9 years. Her sebum plugs usually causes bumps on, and inflame, the skin, before the sebum emerges or can be extracted with a comedo extractor. Occasioanlly, this happens without inflammation.
He said that topical retinoids open pores to help expel the trapped sebum, but only oral treinoin (E.g. accutane) can dwindle sebum production.
We forgot to ask him why the body (on its own) doesn't slack sebum production ? We're assuming the body's ability to detect the inflammation and acne nodes, and to adjust sebum production?