From keratinisation disorders…
An overproduction of corneal cells at the opening of the sebaceous canal (pore) causes it to become blocked and a comedone to form. The sebum is no longer able to flow out as it would normally. It therefore becomes a nutritional source encouraging the growth of certain bacteria (P.acnes).Moreover, this oxygen-deprived environment favours their proliferation.
… to bacterial colonisation
Inflammation then develops through the production of pro-inflammatory cellular mediators. This inflammation is increased by the oxidation of sebum lipids. Spots develop (papules, pustules), and in the more severe cases, turn into nodules and nodular cysts.