Updated November 25, 2014.

Definition:

The bacterium responsible for inflamed acne breakouts. Propionibacteria acnes (P. acnes) are normal residents of the skin, and are generally harmless. But, when pores become engorged with excess oil and dead skin cells, it creates an anaerobic environment where P. acnes can thrive.

P. acnes triggers inflammation within the pore, creating a papule, pimple, or cyst. Reducing the P. acnes population is an important step in controlling acne.

Also Known As: P. acnes, propioni bacteria.