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SUMMARY POINTS
What’s Important?
Oxidation of squalene in sebum leads to comedones and milia.
Oxidized squalene (squalene peroxides) has deleterious effects on skin including aging.
The Baumann Skin Type Indicator Questionnaire can accurately predict sebum secretion rates.
The average sebum production rate is 1 mg/10 cm2 every 3 hours.
What’s New?
Oily skin is divided into normal oily skin and very oily skin.
Normal oily skin has normal sebum secretion rates.
Botulinum toxin Type A reduces sebum production.
Various cannabinoids affect sebum production differently.
What’s Coming?
PPAR and retinoid X receptor agonists and antagonists may be developed topically to control sebum production.
The effect of diabetes medications and insulin-like growth factor-1 (IGF-1) on sebum secretion is yet to be established.
Autophagy regulates sebum production and is suppressed by testosterone as well as IGF-1 and increased by vitamin D. Development of products that increase autophagy in sebocytes may lead to agents to decrease skin oiliness.
More data are needed to compare differences in sebum secretion rates among different ethnicities.
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Sebum is a substance produced by the sebaceous gland (SG) that may follow the idiom “too much of a good thing can hurt you.” Healthy skin requires a normal amount of sebum production. The average rate of sebum production in adults is approximately 1 mg/10 cm2 every 3 hours.1 Production of less than 0.5 mg/10 cm2 every 3 hours results in dry skin while production of over 1.5 mg/10 cm2 every 3 hours results in very oily skin. Neither dry nor very oily skin is desirable. Therefore, the goal is a sebum production rate between 0.6 mg and 1.4 mg/10 cm2 every 3 hours.
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Sebum production plays an important role in skin hydration by producing lipids, glycerol, and other components necessary for skin hydration and protection. Sebum supplies lipids to the surface of the epidermis that aid in fortifying the skin barrier and preventing transepidermal water loss (TEWL). Sebum contains the lipophilic antioxidants vitamin E and coenzyme Q10, which protect the skin from free radicals.2
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Excess sebum production produces very oily skin and contributes to the formation of comedones. With continuing advances in understanding the physiology and molecular biochemistry of SGs and lipid metabolism, scientists may soon be able to manipulate sebum secretion and oily skin. This chapter will focus on the various known causes of oily skin and their implications, a dermatologist-developed taxonomy for oily skin types, and the available treatments for oily skin.
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NOMENCLATURE OF OILY SKIN TYPES
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The Baumann Skin Typing System (BSTS) uses the expression “oily skin” differently than the classic skin type system of dry, normal, oily, and combination skin (see Chapter 10, The Baumann Skin Typing System). “Oily skin” in the BSTS denotes the skin produces an adequate or excessive amount of sebum. Oily skin in this classification has two ...