An improper diet that includes too many soft drinks, spicy and fried food and snacks with high iodine content
Pores clogged by dirt or pollution
Hormonal changes due to menstruation
Genes - blame it on the folks
There are oil glands on your chest, face and back numbering in the thousands. In fact, between the nose and cheek areas there are as many as two thousand oil glands every square inch. The function of these oil glands is to lubricate the skin by producing oil, or sebum. Oil that is produced in the glands flows through follicles or tiny ducts to the surface of the skin. It usually starts far beneath the surface of the skin. A
blemish (or internal lump) begins about 2 to 3 weeks before it appears on your skin's surface. Acne first begins to form in your sebaceous hair follicles. You know this as "pores", the tiny holes on your skin. Deep within each hair follicle, sebaceous glands generate sebum, the oil that keeps your skin soft, moist and pliable. As part of your skin's renewal process the old cells die and are shed off. Normally, this cell shedding process happens gradually, and fresh new skin takes its place.
The trapped oil begins to form a lump as your skin continues its normal oil production. Your body's natural defense system then sends an army of white blood cells to attack the bacteria. The whole process takes around 2 to 3 weeks, resulting in a pimple.