What's the vehicle anyhow?, page-107

it's pretty sh1tty nomenclature, all acne is an inflammatory condition by definition. there are a bunch of articles, this one is fairly approachable.

"Comedones — Comedones are considered non-inflammatory acne lesions and may be open or closed. Closed comedones or whiteheads are small plugged follicles, the contents of which are not exposed to the skin. Open comedones or blackheads are small follicles with dilated openings to the skin allowing oxidation of the debris within the follicle leading to the black color. Though many believe these lesions represent dirt, they cannot be washed away and are not representative of poor hygiene.

Inflammatory acne — When lesions become red and/or tender bumps they are termed papules. These can fill with purulent material forming pus bumps or pustules. Papules and pustules represent inflammatory acne lesions, which originate as comedones."