Acne vulgaris (or simply acne) is a long-term skin disease that occurs when hair follicles become clogged with dead skin cells and oil from the skin. It is caused by an interaction between hormones, skin oils, and bacteria, which results in the inflammation of hair follicles. Genetics is thought to be the cause in 80% of cases. 

Acne primarily affects skin with a greater number of oil glands, including the face, upper part of the chest, and back. Acne is commonly classified by severity as mild, moderate, or severe. This type of categorization can be an important factor in determining the appropriate treatment regimen.

Pigmented scar is a common but misleading term, as it suggests the colour change is permanent. Often, this can be prevented by avoiding aggravation of the nodule. These scars can fade with time. However, untreated scars can last for months, years, or even be permanent if deeper layers of skin are affected. Daily use of SPF 15 or higher sun protector can minimize pigmentation associated with acne.