There are multiple factors which could be causing your acne, it is usually due to one or more of the following:

Fluctuating hormone levels
Like with teenage acne, adult acne is also hormone-dependent. In the older woman, it can occur at the time of peri-menopause, menopause or any hormonal imbalance which can lead to breakouts. Women often experience fluctuating hormones during their periods, pregnancy or after starting or discontinuing birth control.

Stress
Researchers have found a link between stress and acne flare-ups. In response to stress, our bodies produce more androgens (male hormones). These hormones stimulate the oil glands and hair follicles in the skin, which in turn can lead to acne. This is the reason acne can persist in people with high-level or ongoing stress.

Family history
Other research studies suggest that some people may have a genetic predisposition to acne. If a close blood relative, such as a parent, brother or sister has acne, you are more likely to get adult acne.

Hair and skincare products
Use of rich or greasy skin products and/or sunscreens can clog the pores and trigger acne. Acne resulting from hair products commonly affects the forehead and we refer to it as pomade acne. You can counter this type of acne by using oil-free or non-comedogenic skin products.

Medication side effect
Acne is a common side effect of some medicines. It is important that you notify your doctor about any medication you might be taking including herbal treatments. Common offending medication includes treatment for epilepsy, tuberculosis, depression, steroids, halogens and B vitamins.

Undiagnosed medical condition
Sometimes acne is a sign of an underlying medical condition. Once the medical condition is diagnosed and treated, the acne often clears.