First let me say a little about what scientists believe causes acne
and then I'll explain why they might showing up where you are describing and how to prevent their future formation. Scientists believe that there are four major factors that lead to acne: 1) increased production of a protein on the skin called keratin which leads plugging of follicles and the creation of "whiteheads;" 2) increased production of an oily substance called sebum that helps to plug the follicles; 3) breakage of the pimples which causes inflammation of the skin; 4) and finally a bacteria called p. acnes that lives on the skin and helps to worsen the inflammation. A whitehead is one form of acne and called a closed comedo. It is the result of the plugged follicle containing the excess keratin and sebum. Whiteheads will form only in places with well-developed sebaceous glands such as the face, neck, chest, and back. The distribution of acne that you are describing is likely simply related to where the most glands are. And so it is very possible that what you have is simply a cluster of whiteheads, though other dermatological conditions are still possible. Nevertheless, if the cluster looks like a group of whiteheads this is very likely to be so. Your primary care provider or a dermatologist
can better evaluate your symptoms and discuss the further treatment options for you.