Causes of Acne

Three factors contribute to the formation of acne:

1. Overproduction of oil (sebum)
2. Irregular shedding of dead skin cells resulting in irritation of the hair follicles of your skin
3. Buildup of bacteria

Acne occurs when the hair follicles become plugged with oil and dead skin cells. Hair follicles are connected to sebaceous glands. These glands secrete an oily substance known as sebum to lubricate your hair and skin. Sebum normally travels up along the hair shafts and then out through the openings of the hair follicles onto the surface of your skin. When your body produces an excess amount of sebum and dead skin cells, the two can build up in the hair follicles and form together as a soft plug, creating an environment where bacteria can thrive.
This plug may cause the follicle wall to bulge and produce a whitehead. Or, the plug may be open to the surface and may darken, causing a blackhead. Pimples are raised red spots with a white center that develop when blocked hair follicles become inflamed or infected. Blockages and inflammation that develop deep inside hair follicles produce lumps beneath the surface of your skin called cysts. Other pores in your skin, which are the openings of the sweat glands onto your skin, aren't normally involved in acne.

Factors that may worsen acne

These factors can trigger or aggravate an existing case of acne:

• Hormones. Androgen's are hormones that increase in boys and girls during puberty and cause the sebaceous glands to enlarge and make more sebum. Hormonal changes related to pregnancy and the use of oral contraceptives can also affect sebum production.
  Hormonal activity, such as menstrual cycles and puberty, may contribute to the formation of acne. During puberty, an increase in sex hormones called androgens cause the follicular glands to grow larger and make more sebum; A similar increase in androgens occurs during pregnancy, also leading to increased sebum production. Use of anabolic steroids may have a similar effect. Several hormones have been linked to acne: the androgens testosterone, dihydrotestosterone (DHT) and dehydroepiandrosterone sulfate (DHEAS), as well as insulin-like growth factor 1 (IGF-I).
  Development of acne vulgaris in later years is uncommon, although the incidence of rosacea, which may have a similar presentation, is increased in older age groups. True acne vulgaris in adult women may be a feature of an underlying condition such as pregnancy, or disorders such as polycystic ovary syndrome, hirsutism, or Cushing's syndrome. Menopause-associated acne (known as acne climacterica) occurs as production of the natural anti-acne ovarian hormones estradiol and progesterone fail, permitting the acnegenic hormone testosterone to exert its effects unopposed.
• Psychological. While the connection between acne and stress has been debated, scientific research indicates that "increased acne severity" is "associated with increased stress levels." The National Institutes of Health (USA) list stress as a factor that "can cause an acne flare."
• Infectious. Propionibacterium acnes (P. acnes) is the anaerobic bacterium species that is widely concluded to cause acne, though Staphylococcus aureus has been universally discovered to play some role since normal pores appear colonized only by P. acnes. Regardless, there are specific clonal sub-strains of P. acnes associated with normal skin health and others with long-term acne problems. It is as yet inconclusive whether any of these undesirable strains evolve on-site in the adverse conditions or are all pathogenically acquired, or possibly both depending on the individual patient. These strains either have the capability of changing, perpetuating, or adapting to, the abnormal cycle of inflammation, oil production, and inadequate sloughing activities of acne pores. At least one particularly virulent strain, though, has been circulating around Europe for at least 87 years. In vitro, resistance of P. acnes to commonly used antibiotics has been increasing, as well. It is unclear if the parasitic mite Demodex, has an effect.
• Certain medications. Drugs containing corticosteroids, androgen's or lithium are known to cause acne.
• Diet. Studies indicate that certain dietary factors, including dairy products and carbohydrate-rich foods — such as bread, bagels and chips, which increase blood sugar — may trigger acne.
  The relationship between diet and acne is unclear as there is no good quality evidence. However, a high glycemic load diet is associated with worsening acne. There is also a positive association between the consumption of milk and a greater rate and severity of acne. Other associations such as chocolate and salt are not supported by the evidence. Chocolate does contain a varying amount of sugar that can lead to a high glycemic load and it can be made with or without milk. There may be a relationship between acne and insulin metabolism and one trial found a relationship between acne and obesity.

Acne myths

Contrary to what some people think, these factors have little effect on acne:

1. Greasy foods and chocolate have proved to have little to no effect on the development or course of acne.
2. Dirty skin. Acne isn't caused by dirt. In fact, scrubbing the skin too hard or cleansing with harsh soaps or chemicals irritates the skin and can make acne worse. Simple cleansing of the skin to remove excess oil and dead skin cells is all that's required.