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Issue
38 — February 2005 |
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38 |
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| Cover
Picture |
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Keratinization
of the duct of the hair follicle |
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Impure skin is often a disorder resulting from oily skin. If excessive amounts
of sebum are produced and a hornification disorder occurs at the same time, this
can lead to impure skin or acne. Small horny plugs are formed and lead to a blockage
of sebum secretion. Comedones, commonly known as blackheads or whiteheads, are
the result.
Acne vulgaris is an inflammatory skin disorder and is the most common type of
skin disease among teenagers. The typical changes in the hormonal production at
this age play a role in the etiology of acne. Further factors leading to the manifestation
of acne are an increase in lipid production by the sebaceous glands, keratinization
disorders, bacterial proliferation and inflammatory responses within the pilosebaceous
unit. In addition, a genetic predisposition, hormonal changes, environmental factors
as well as the use of cosmetics which are improperly used or contain comedogenic
substances also need to be taken into consideration. As acne is a disorder of
the pilosebaceous unit, acne-like changes generally occur in skin areas which
contain a high amount of sebaceous glands, in particular the face and upper body.
Our illustration on the left, which gives a schematic representation of the pilosebaceous
unit, shows how sebum is produced by the sebaceous gland, is transported to the
skin’s surface via the duct of the hair follicle and is secreted through
the follicle opening. On the skin’s surface, sebum naturally spreads in
dependence on the skin’s hydration and environmental influences. The healthy
hair follicle is not influenced by the sebum production, it remains intact.
The drawing on the right depicts a sebaceous gland under conditions leading to
the formation of comedones. The sebaceous gland is intact or possibly enlarged
and overproduces large amounts of sebum. If the skin is acne-prone, abnormal keratinization
and desquamation of the keratinocytes lining the follicle results in the formation
of excessive keratinous debris which combined with sebum can clog the opening
of the hair follicle.
The sebum cannot reach the skin’s surface and thus comedones are formed
(open comedo – blackhead; closed comedo – whitehead). In the course
of time, pus-filled pustules may develop from the comedones. This takes place
when the follicular canal is ruptured and accumulated sebum is emptied into the
adjacent tissue, thus eliciting inflammatory responses. In addition, Propionibacterium
acnes may easily increase thus leading to additional inflammatory responses. If
the inflamed lesions spread into the surrounding tissue, large nodules may be
formed which can lead to scar formation.
