Acne occurs when hair follicles become clogged.
Many factors can contribute to acne along the chin line, including genetics, certain conditions, and some medications. You can treat chin-line acne with over-the-counter products. However, in more severe cases, your doctor may prescribe medication. Depending on the type of treatment and the severity of the acne, it may take several weeks to notice improvement.
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.