Adult acne offers the same causes as acne in our teens. Gavali Advance Skincare Environmental toxins like dust and exhaust fumes can impact on the skin gravely. Stress is believed to be another factor for adult acne breakout. Though it may not directly cause acne it can worsen flare ups. Days are not easy with all the current family ad work responsibilities thrown for us daily. Stress 's almost impossible to avoid sometimes. Find to help relax. Another possible cause of adult acne is hormonal changes in pregnant and menopausal women. When women go though these changes, it effects their mood, appetite, and even their skin. Certain medications can also cause breakouts.