In normal skin, oil glands under the skin, known as sebaceous glands, produce an oily substance called sebum. The sebum moves from the bottom to the top of each pore and then spills out onto the surface of the skin, taking with it sloughed-off skin cells.

The exact cause of acne is unknown. Factors contributing to the production of acne are overactive sebaceous glands producing excess oil. There is an increase cell production within the pores. The cells become sticky and instead of flowing onto the skin where they exfoliate, these sticky cells adhere to each other, remain in the pore and form a plug called a comedone. There are bacteria (Propionibacterium acnes) which inhabit the pores. These bacteria induce an inflammatory response resulting in a pimple or cyst.

Hormones, menstruation, genetic factors and emotional stress can produce acne or cause it to flare.

Foods producing a high glycemic load (or high sugar levels in the blood) such as white potatoes, white bread, cookies, watermelon, doughnuts, cereals, and dates may cause acne to flare. Low glycemic index food such as low-fat yogurt, apples, kidney beans and most vegetables and proteins are a better choice of foods to help control acne flares.

It is important for patients not to pick or scratch at individual lesions because it can make them inflamed and can lead to long-term scarring.