Whether a person develops comedones, papules, pustules, cysts, or a combination of these lesions depends on how severely the hair follicles are clogged and inflamed. The worse the inflammation, the more severe the acne lesion. For example, comedones, which are basically enlarged, clogged hair follicles, form before the hair follicles become inflamed or in the earliest stages of inflammation. Comedones contain sebum, dead skin cells, and bacteria that are trapped in the follicles, but comedones do not contain pus, nor are they red or swollen. That is why comedones are the least severe type of acne lesion.

Since comedones do not contain pus, they are quite small. All comedones have either a white or black tip. Hence, comedones are commonly known as whiteheads or blackheads.