Acne is defined as a skin condition which occurs when hair follicles get plugged with sebum and dead skin cells. It is a common condition in teenagers and appears on the face, forehead, chest, upper back and shoulders.

Acne commonly affects teenagers and young adults. It can affect other age groups, but is more common in adolescence. About 70-90 % cases are present in teenagers.

Acne is typically caused by many factors like genetics, bacteria, excessive oil production, and changes in level of hormones. Certain factors can aggravate acne like
- Medications like testosterone, corticosteroids
- Diet like skim milk, chips, bread
- Excess production of hormones called androgens
- Stress

The parts of the body commonly affected by acne include
- Upper back
-Chest
-Forehead
-Face
-Shoulders
Since skin of these parts contain most sebaceous glands, they are affected commonly by acne.

Acne results due to blockage of hair follicles. It results in formation of microcomedones due to accumulation of skin cells in the hair follicle. Changes can result in formation of comedones, papules, pustules, nodules and scarring. Hyperpigmentation of skin can occur.