What causes acne explained
 
CAUSES OF ACNE

Introduction

Acne is a common skin disorder affecting the face, neck, chest and back affecting 70% to 80% of young adults. Though not physically disabling, acne can cause severe emotional stress due to permanent facial scarring and due to its persistence. Additionally, it occurs during adolescence - a difficult period of growth and development for any young adult. Appropriate treatment can improve the lives of affected individuals dramatically.

The primary lesions of acne are the comedones. Comedones are plugs of sebum and keratin lodged in the follicular ducts. These comedones are non-inflammatory, but if they rupture the follicular wall, an inflammatory reaction to the sebum produces papules, pustules and cysts. The anaerobic bacteria, propionibacteria, inhabiting the microenvironment of the follicle, also promote non-inflammatory lesions into inflammatory lesions. The immune system recognizes the bacteria in the ruptured hair follicles and responds to them to try and destroy the bacteria. These inflammatory lesions may produce scars if the inflammation is intense enough.

The question is, what causes the increased production of sebum and why does this eventually lead to acne? Several factors may be involved.

Androgens

Numerous studies have shown that androgens are a major factor in the production of acne. Most androgens are produced by the gonads and adrenal glands, but some are also produced locally within the sebaceous glands from the adrenal precursor hormone called DHEA.

Though the cellular or molecular mechanism by which androgens stimulate sebum production is not fully understood it is well known that major androgens, like testosterone, interact with the sebaceous glands through androgen receptors. These androgen receptors are located on cells of the basal layer of the sebaceous glands and the outer root sheath keratinocytes of the hair follicle.

The important role of androgens in stimulating sebum production is shown by the following five pieces of clinical evidence:

  • The development of early acne in the prepubertal period occurs with higher serum levels of DHEAS, a precursor of testosterone.
  • Androgen-insensitive subjects lacking functional androgen receptors do not produce sebum and do not develop acne.
  • Androgen producing tumors of the ovary or adrenal glands are often associated with acne.
  • Systemic administration of testosterone and DHEAS increases the size and secretion of sebaceous glands.
  • Severe acne is often associated with higher serum androgen levels.

It is therefore clear that hormones are involved in acne development.

Stress induced acne

In women, onset of acne coincides with menarche but its prevalence varies widely. An interesting development has been the identification of low grade persistent acne in women over 25 years of age, some in their forties. This is believed to be due to stress induced secretion of adrenal androgens. Emotional stress has been anecdotally linked to acne though an objective assessment has been lacking until recently. The latest studies on stress induced acne do show a statistical correlation.

Growth hormones in acne

Growth hormone is produced by the pituitary glands and acts on the liver and peripheral tissues to stimulate the production of insulin growth factor (IGF) also known as somatomedians. IGF comes in two forms, the more prevalent IGF-1 and also IGF-2. IGF is a known promoter of keratinocyte activity. IGF-1 can promote increased sebaceous gland oil production. Because of this property, growth hormone may be involved in acne development. Acne is most widespread during adolescence when growth hormone secretion and IGF-1 serum levels are at their highest. Also, IGF-1 molecules can be produced locally within the skin where they can interact with the IGF receptors on the sebaceous glands to increase sebum production. Consequently, the growth that occurs in teens may contribute to the development of acne

Diet as a cause of acne

Diet as a cause of acne has traditionally been dismissed as myth. However, the near absence of acne in non-westernized cultures and the presence of acne in western or westernized cultures suggests that diet and the environment could be causes. One study suggests that the high glycemic diets of the West could cause acne by producing hyperinsulinemic states.

Genetic factors

Another factor, facial oiliness or seborrhea, is believed to be a pre-condition for acne. The degree of oiliness that an individual experiences may be partly due to their genetic make up. It seems likely that some genes code for a higher level of sebaceous gland activity and oil production. Genes may also play a role in the nature of the sebum that is produced. Some genes code for higher levels of cholesterol production. Cholesterol is a relatively sticky molecule. When there is more cholesterol produced by the sebaceous glands, the oils and dead cells from the hair follicle canal are more likely to stick together and form the nucleus of a sebum plug.

Seborrhea most commonly occurs on the face, but with the exception of isotretinoin, no other drug is able to inhibit sebum production.