Acne is a skin condition, also known as acne vulgaris, that occurs when your hair follicles become plugged with oil and dead skin cells. It often causes whiteheads, blackheads and usually appears on the face, forehead, chest, upper back and shoulders. Acne is most common among teenagers, though it affects people of all ages. Common triggers include:

• High humidity and sweating
• Inadequate face washing
• Occlusive cosmetics, cleansers, lotions, and clothing
• Hormonal changes that occur with pregnancy or the menstrual cycle
• Polycystic ovary syndrome
• Association with milk products and high-glycemic diets.
• Some drugs and chemicals (eg. corticosteroids, lithium, phenytoin, isoniazid)