When whiteheads and blackheads become infected with bacteria, called Propionibacterium acnes, it leads to inflammatory acne. Regular bacteria is found in most whiteheads and blackheads, but P. acnes is attracted to the closed, oily environment. This bacteria makes acne more difficult to treat. The four different pimple types that characterize inflammatory acne are papules, pustules, nodules and cysts.
First, let’s talk about what causes acne. Pimples form when the oil and dead skin cells on your skin combine to form a plug that blocks the pores. “As the P. acnes bacteria that naturally live on skin overgrow within this plugged follicle, the area becomes inflamed and this is when you start to see papules, pustules, and cystic lesions,” RealSelf dermatologist Sejal Shah, M.D., tells SELF. The treatments ahead work to exfoliate away dead skin cells, suck up excess oil, stop inflammation, and kill the P. acnes bacteria. There are even a few treatments that target hormonal acne specifically.

Retinoids – Recommended for people with moderate to severe acne, retinoids can unclog your pores, allowing for your other medicated acne treatments to penetrate deeper. They can reduce your potential for outbreaks and the formation of acne scarring2. You can also use a retinoid cream directly as a treatment after your face cleanse, or even take it in the form of a retinoid pill to treat oil/sebum production and to treat inflammation and acne-causing bacteria.
This inflammatory cascade typically leads to the formation of inflammatory acne lesions, including papules, infected pustules, or nodules.[1] If the inflammatory reaction is severe, the follicle can break into the deeper layers of the dermis and subcutaneous tissue and cause the formation of deep nodules.[1][66][67] Involvement of AP-1 in the aforementioned inflammatory cascade leads to activation of matrix metalloproteinases, which contribute to local tissue destruction and scar formation.[44]
Acne appears when a pore in our skin clogs. This clog begins with dead skin cells. Normally, dead skin cells rise to surface of the pore, and the body sheds the cells. When the body starts to make lots of sebum (see-bum), oil that keeps our skin from drying out, the dead skin cells can stick together inside the pore. Instead of rising to the surface, the cells become trapped inside the pore.
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