Stress can have physiological effects on the body, including stimulating a hormone that encourages the sebaceous glands to produce more oil, increasing the chances of breaking out. Besides stress, there are many things that contribute to inflamed and non-inflamed acne.
If your parents or someone in your family had acne, your risk for having acne is higher. This is due to the P-Acnes bacteria which is hereditary.
As hormone levels in the teen years surge, the onset of acne occurs. Certain hormones trigger the sebaceous gland to produce more oil, resulting in more clogged pores. Monthly hormonal fluctuations as well as those experienced at the onset of menopause contribute to acne. Certain drugs and steroids, androgens, lithium and barbiturates are known to stimulate acne.