Genetics play a big part in who gets acne and how severely, but each blemish can be blamed on some combination of sebum production, a bacteria called Propionibacterium acnes (P. acnes), plugged follicles, and inflammation. Finding a good treatment is really about finding the right combination of ingredients to troubleshoot each of those issues. Some factors that might worsen acne include hormones, certain medications, diet and stress.
Pimples are raised red spots with a white center that develop when blocked hair follicles become inflamed or infected with bacteria. Blockages and inflammation that develop deep inside hair follicles produce cystlike lumps beneath the surface of your skin. Other pores in your skin, which are the openings of the sweat glands, aren't usually involved in acne.