Celtnet Medicine: The Biology of Acne
The Biology of Acne
(also known as Seborrhea)

Acne Vulgaris, also known as seborrhea or seborrheic dermatitis is an inflammatory disease of the skin, caused by changes in the pilosebaceous units (skin structures consisting of a hair follicle and its associated sebaceous gland). Acne lesions are commonly referred to as pimples, spots, or zits.


Acne Pimples
The image above shows an example of human skin with several acne lesions. These are both infected and show skin damage and infiltration by white blood cells.

Acne develops because of impairments of the functioning of skin glands (dermis and epidermis), notably due blocked hair follicles and obstructed sebaceous glands. nder normal conditions the sebaceous glands release oil that comes up through your pores onto the skin surface. This release keeps your skin moist and lubricated for protection from the environment. But if these become blocked or plugged the oil that they exude becomes trapped. This is toxic to the nearby cells and results in a growth or pimple that start to increase in size as more toxic oil tries to reach the surface of your skin.

Causes

Acne is caused when hair follicles or the oil-producing (sebaceous) glands in your skin become contaminated with toxic matter which can contain dirt, dead skin, excess sebum oil, acid waste, bacteria and toxic matter. This occurs when the sebaceous glands become plugged with keratin and sebum during a process known as hyperkeratinizaton the excess production of keratin. Most typically this occurs in teenagers during the maturation of the skin following puberty. Puberty also produces an increase in androgen (sex hormone) production and this increases the skin's production of sebum. This increased sebum production becomes prone to infection, leading to a build-up of bacteria. The immune system attacks the bacteria and filters the pus into segregated pockets that can be from 0.2mm up to 10mm underneath the intact skin surface epidermis. Surface infections are called zits whereas the deeper ones are called pustules.

As bacteria grow within the infected glands this induces swelling which causes itching and discomfort. Many sufferers attempt to alleviate this discomfort by scratching or crushing the acne with their fingers. This results in the damage of underlying layers of skin which destroys the integrity of the dermis and creates a weak zone to be attacked by bacteria. This results in an immune response resulting in more acne draining into the surrounding sebaceous glands. Bruising of the surrounding tissue can also result in scar formation and the deformation of the fine structures of the dermis so that its function is impaired which can create long-term havens for bacteria, exacerbating the problem. This can result in some sebaceous glands growing without any kind of channel through to the surface of the skin. Others swell by up to 20 times their original size. when these are drained, the walls of the enlarged gland are still intact under the skin and free to accumulate sebum and may or may not become infected. Sometimes a pustule forms around a hair strand that has not reached the surface and that has grown more than a centimetre curled inside the sebaceous gland.

Acne occurs most commonly in adolescence, affecting more than 85% of adolescents, but it can continue into adulthood though it tends to diminish over time and becomes less of a problem from the mid 20s onwards. There is, however, no way to predict how long it will take for it to disappear entirely, and some individuals will continue to suffer from acne decades later, into their thirties and forties and even beyond.

The name acne itself is derived from the Greek, άκμή (literally 'skin eruption').

Several factors are known to be linked to acne:

  • Family history
  • Hormonal activity, especially menstrual cycles, puberty, menopause and pregnancy
  • Stress, which can cause increased output of hormones from the adrenal (stress) glands
  • Hyperactive sebaceous glands, which can be secondary to the three hormonal causes, above
  • Accumulation of dead skin cells, particularly in the case of corneocytes blocking hair follicles
  • Accumulation of bacteria in the pores, to which the body becomes 'allergic'
  • 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 high levels of chlorine compounds, particularly chlorinated dioxins, can cause severe, long-lasting acne, known as Chloracne

There are also possible dietary factors and increase in the severity of acne has been linked to:

  • Consumption of consumption of partially skimmed milk, instant breakfast drink, sherbet, cottage cheese and cream cheese which may be due to some latent bovine hormones in the milk products.
  • Seafood often contains high levels of iodine and this halogen can trigger acne attacks
  • High Glycaemic Index foods (ie foods high in refined sugars) have been linked to acne in that populations whose diets are low in refined sugars tend not to develop acne

Prevention

Prevention of Acne is difficult, but as the diesease is caused by hormonal changes, stress and dietary factors healthy lifestyle, low toxin low sugar natural diets, proper levels of exercise, situational organisation and improvements in stress levels, decent hygiene, gentle skincare may aid in reducing the severity of acne.

Treatment

In terms of medical or chemical treatments, generally speaking at least, most successful treatments give little improvement within the first week or two; and then the acne decreases over approximately 3 months, after which the improvement starts to flatten out. Treatments that promise improvements within 2 weeks are likely to be largely disappointing. Short bursts of cortisone, quick bursts of antibiotics and many of the laser therapies offer a quick reduction in the redness, swelling and inflammation when used correctly, but none of these empty the pore of all the materials that trigger the inflammation.

Treatments that have proven succesful include:

Exfoliation: This is the destruction of the top layer of skin cells at the microscopic level and can be done using an abrasive cloth or a liquid scrub, or chemically with compounds such as salicylic acid and glycolic acid.

Topical Bacterioidals: this generally involves the applicaton of creams containing benzoyl peroxide. Typically a gel or cream containing benzoyl peroxide is rubbed, twice daily, into the pores over the affected region. Bar soaps or washes may also be used and vary from 2 to 10% in strength. Benzoyl peroxide acts to dissolve the keratin plugging the pores as well as killing the bacterium, Propionibacterium acnes, the main cause of acne.

Topical antibiotics: here antibiotics — typically erythromycin, clindamycin, Stiemycin or tetracycline are applied to the skin in creams.

Oral antibiotics: antibiotics such as erythromycin or one of the tetracycline antibiotics (tetracycline, the better absorbed oxytetracycline, or one of the once daily doxycycline, minocycline or lymecycline) have been used to destroy the P acnes bacteria but they do not treat the underlying causes of the problem and are becoming less useful as antibiotic resistant forms of the bacterium evolve.

Hormonal treatments: in women, at least, acne can be improved with hormonal treatments. The common combined oestrogen/progestogen methods of hormonal contraception have some effect, but the anti-testosterone, Cyproterone, in combination with an oestrogen (Diane 35) is particularly effective at reducing androgenic hormone levels.

Topical retinoids: Topically-applied retinoids such as tretinoin (brand name Retin-A), adapalene (brand name Differin) and tazarotene (brand name Tazorac), which are related to vitamin A, influence the cell creation and death lifecycle of cells in the follicle lining and thus they normalize the follicle life cycle by prevent the hyperkeratinization of these cells that can create a blockage.

Oral Retinoids: Daily oral intake of vitamin A derivatives like isotretinoin (marketed as Accutane, Sotret, Claravis) over a period of 4–6 months reduces the secretion of oils from the sebaceous glands. These drugs show much longer-term effects than oral antibiotics and can often clear-up acne on a permanent basis.

Phototherapy: Sunlight can cure acne short-term but prolonged exposure to sunlight actually worsens acne as it leads to increased secretion of oils as the skin attempts to protect itself from sun damage. However, intense violet light (405-420nm) generated by purpose-built fluorescent lighting, dichroic bulbs, LEDs or lasers has recently been successfully employed to treat acne. Used twice weekly, this has been shown to reduce the number of acne lesions by about 64%. The treatment apparently works even better if used with red visible light (660 nanometer) resulting in a 76% reduction of lesions after 3 months of daily treatment for 80% of the patients. This is because P acnes contains a photophore, Coproporphyrin III, which is activated by these wavelengths of light producing free radicals that destroy the bacterial cells.

Preferred treatments by types of acne vulgaris

  • Comedonal (non-inflammatory) acne: local treatment with azelaic acid, salicylic acid, topical retinoids, benzoyl peroxide.
  • Mild papulo-pustular (inflammatory) acne: benzoyl peroxide or topical retinoids, topical antibiotics (such as erythromycin).
  • Moderate inflammatory acne: benzoyl peroxide or topical retinoids combined with oral antibiotics (tetracyclines). Isotretinoin is an option.
  • Severe inflammatory acne, nodular acne, acne resistant to the above treatments: isotretinoin, or contraceptive pills with cyproterone for women with virilization or drospirenone.