Susceptibility to acne is primarily genetic in 80% of cases. The roles of diet and cigarette smoking in the condition are unclear, and neither cleanliness nor exposure to sunlight are associated with acne. In both sexes, hormones called androgens appear to be part of the underlying mechanism, by causing increased production of sebum. Another common factor is the excessive growth of the bacterium Cutibacterium acnes, which is present on the skin.

This article explains in more detail the causes and risk factors for chin-line acne. It also discusses treatment options, when to see a doctor, and more.
What causes acne along the chin line? Your skin is naturally lubricated by oils produced by the sebaceous glands. These glands direct oils to the skin’s surface through the pores of the hair follicle. Excess dirt, hair, and dead skin cells can clog these pores.

Bacteria living on the skin’s surface can also multiply in clogged pores, causing inflammation. This can eventually lead to the formation of pimples or blackheads.