| Acne develops as a result of blockages in follicles. Hyperkeratinization and formation of a plug of keratin and sebum (a microcomedo) is the earliest change. Enlargement of sebaceous glands and an increase in sebum production occur with increased androgen ( DHEA-S ) production at adrenarche . The microcomedo may enlarge to form an open comedo ( blackhead ) or closed comedo ( whitehead ). In these conditions the naturally occurring largely commensual bacteria Propionibacterium acnes can cause inflammation , leading to inflammatory lesions ( papules , infected pustules, or nodules) in the dermis around the microcomedo or comedo, which results in redness and and may result in scarring or hyperpigmentation.
Exactly why some people get acne and some do not is not fully known. It is known to be partly hereditary. Several factors are known to be linked to acne:
- Family/Genetic history. The tendency to develop acne runs in families. For example, school-age boys with acne have other members of their family with acne. A family history of acne is associated with an earlier occurrence of acne and an increased number of retentional acne lesions.
- Hormonal activity, such as menstrual cycles and puberty . During puberty, an increase in male sex hormones called androgens cause the glands to get larger and make more sebum.
- Stress, through increased output of hormones from the adrenal (stress) glands Although modern tests have said otherwise and point to this not being a cause.
- Hyperactive sebaceous glands , secondary to the three hormone sources above.
- Accumulation of dead skin cells.
- Bacteria in the pores. Propionibacterium acnes (P. acnes) is the anaerobic bacterium that causes acne. In-vitro resistance of P. acnes to commonly used antibiotics has been increasing.
- Skin irritation or scratching of any sort will activate inflammation.
- Use of anabolic steroids .
- Any medication containing halogens (iodides, chlorides, bromides), lithium , barbiturates , or androgens .
- Exposure to certain chemical compounds. Chloracne is particularly linked to toxic exposure to dioxins , namely Chlorinated dioxins .
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). In addition, acne-prone skin has been shown to be insulin resistant.
Development of acne vulgaris in later years is uncommon, although this is the age group for Rosacea which may have similar appearances. True acne vulgaris in adults may be a feature of an underlying condition such as pregnancy and disorders such as polycystic ovary syndrome or the rare Cushing's syndrome . Menopause-associated acne occurs as production of the natural anti-acne ovarian hormone estradiol fails at menopause. The lack of estradiol also causes thinning hair, hot flashes, thin skin, wrinkles, vaginal dryness, and predisposes to osteopenia and osteoporosis as well as triggering acne (known as acne climacterica in this situation).
A recent study, based on a survey of 47,335 women, did find a positive epidemiological association between acne and consumption of partially skimmed milk , instant breakfast drink, sherbet, cottage cheese , and cream cheese. The researchers hypothesize that the association may be caused by hormones (such as several sex hormones and bovine IGF-I ) present in cow milk. Though there is evidence of an association between milk and acne, the exact cause is unclear. Most dermatologists are awaiting confirmatory research linking diet and acne but some support the idea that acne sufferers should experiment with their diets, and refrain from consuming such fare if they find such food affects the severity of their acne.
Seafood often contains relatively high levels of iodine . Iodine is known to make existing acne worse but there is probably not enough to cause an acne outbreak. Still, people who are prone to acne may want to avoid excessive consumption of foods high in iodine.
High carbohydrates/High GI
It has also been suggested that there is a link between a diet high in refined sugars and other processed foods and acne. The hypothesis is that rapidly digested carbohydrate food such as white bread and refined sugars produces an overload in metabolic glucose that is rapidly converted into the types of fat that can build up in sebaceous glands. According to this hypothesis, the startling absence of acne in non-westernized societies could be explained by the low glycemic index of these cultures' diets. Others have cited possible genetic reasons for there being no acne in these populations, but similar populations shifting to these diets do develop acne. [ citation needed ] Note also that the populations studied consumed no milk or other dairy products. Further research is necessary to establish whether a reduced consumption of high-glycemic foods (such as soft drinks, sweets, white bread) can significantly alleviate acne, though consumption of high-glycemic foods should in any case be kept to a minimum, for general health reasons. Avoidance of 'junk food' with its high fat and sugar content is also recommended. The University of Pennsylvania and the US Naval Academy conducted experiments that fed subjects chocolate or a bar with similar amounts of macronutrients (fat, sugar etc.) and found that consumption of chocolate, frequent or not, had no effect on the developing of acne.
A 2005 systematic review found "surprisingly little evidence exists for the efficacy or lack of efficacy of dietary factors, face-washing and sunlight exposure in the management of acne." A study in November 2006 in Australia gave a 50% reduction in 12 weeks in mild-moderate facial acne by introducing its subjects to a high protein, low GI diet.
The American Medical Association says chocolate does not contribute to acne.
A recent study shows that a diet high enough in sugars triggers the liver to convert these sugars into lipid; as a side-effect this stops production of Sex hormone binding globulin - a chemical which reduces the level of testosterone in the blood. Since high testosterone levels generally trigger acne, the researchers believe that this can be a cause.
Vitamins A and E
Studies have shown that newly diagnosed acne patients tend to have lower levels of vitamin A circulating in their bloodstream than those that are acne free. In addition people with severe acne also tend to have lower blood levels of vitamin E.
Acne is not caused by dirt. This misconception probably comes from the fact that blackheads look like dirt stuck in the openings of pores. The black color is not dirt but simply oxidised keratin. In fact, the blockages of keratin that cause acne occur deep within the narrow follicle channel, where it is impossible to wash them away. These plugs are formed by the failure of the cells lining the duct to separate and flow to the surface in the sebum created there by the body.