• No proof exists that chocolate causes acne flareups.Chocolate Squares image by lefebvre_jonathan from Fotolia.com
  
  While acne breakouts tend to be most common in teens ages 16 to 18, 15 percent of women and 5 percent of men continue to experience symptoms of acne in their adult lives. Acne appears when oil, or sebum, and dead skin cells clog hair follicles.
  
  

Hormones

• Hormones play a part in the increased production of sebum. The male hormone testosterone is produced in teenagers of both genders. Adult women experience hormonal shifts in their adult lives that play a part in acne. Sometimes women experience breakouts two to seven days before their menstrual period. Pregnancy also increases the production of hormones in the body.
  
  

Bacteria

• Not to be confused with dirt, which does not cause acne, bacteria plays a role in breakouts. While the exact role of bacteria in acne is unclear, bacteria appear during puberty when acne outbreaks are common. The amount of bacteria found on the skin does not play a part in the severity of the breakout. One bacterium, Proprionbacterium acnes, produces active enzymes and irritants that contribute to acne.
  
  

Medications

• Medications that make hormones shift in the body could cause or aggravate an acne breakout. Oral steroids can cause acne, and anabolic steroids can lead to severe acne. Birth control pills may also be to blame for breakouts. Contraceptives that work by reducing sex hormone binding globulin, or SHBG, aggravate acne in the females taking them.
  
  

Medical Conditions

• Certain diseases or conditions, both rare and common, could be the culprit of sporadic acne breakouts. Stress and depression increase levels of sebum-producing hormones. Women with polycystic ovaries have higher levels of androgenic hormones, a cause of acne. A very rare condition known as sterol hydroxylase deficiency also leads to acne. Another rare condition, known as Cushing's disease, causes acne because high levels of the adrenocorticotrophic hormone causes excessive male hormones.
  
  

Other Factors

• Cosmetic products like moisturizers, foundation and pomade products contain certain ingredients that may trigger or inflame acne. These ingredients can clog the pores or cause the skin to generate excessive amounts of oil. Other factors possibly at blame could include things like headbands that apply constant pressure to an area of the skin.