Acne is a chronic, inflammatory skin disease that causes spots and pimples, especially on the face, arms, back, neck, chest and shoulders.
It manifests as lesions on the skin, such as blackheads, pimples, cysts and nodules.
It usually occurs during puberty, when the sebaceous glands become active, but can occur at any age. Acne is not dangerous, but it can leave scars on the skin.
The sebaceous glands produce excess sebum, the production of which is stimulated by the adrenal hormones.
At least 85% of people between the ages of 12 and 24 experience acne.