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The Science of Sebum and the Sebaceous Glands

Écrit par : Dr. Leslie Baumann

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Temps de lecture 11 min

Sebum is a natural oil that everybody produces at different levels depending on their skin type. If you have ever looked in the mirror and noticed a shiny glow across your face, you have seen your skin's sebum. While oily skin can feel like a nuisance, and can clog pores, the oil on your skin – sebum – is actually beneficial in many ways. Read on to learn all about the science behind oily skin and how sebum impacts your skin health. Be sure to take the Baumann Skin Type quiz, because most people guess their skin type incorrectly! Find out if your skin is oily or dry for free today!

What is sebum

What is sebum?

Sebum is an oily substance produced by small glands in the skin called sebaceous glands. Sebum coats the skin’s surface and provides a protective barrier against the environment. The main role of sebum is to keep the skin supple and prevent water loss. It also transports antioxidants like vitamin E to the skin’s surface. The average adult produces around 1 mg of sebum per 10 cm2 of skin every 3 hours. This naturally produced oil is essential for healthy skin hydration and barrier function.

What are the Sebaceous Glands?

Sebaceous glands are tiny glands found inside hair follicles that produce and secrete sebum. There are sebaceous glands distributed throughout the skin, except for the palms of the hands, soles of the feet, and the lips. The greatest concentration is on the scalp and face. Sebaceous glands are made up of special sebum-producing cells called sebocytes. As sebocytes mature, they accumulate lipids and increase dramatically in size before eventually releasing sebum onto the skin’s surface. 

What is sebum made of?

What is Sebum made of?

Sebum contains a mixture of lipids, including triglycerides, wax esters, squalene, free fatty acids, and small amounts of cholesterol. Two of the main players are triglycerides and squalene. Triglycerides make up the largest proportion of sebum – around 57.5%. They are broken down by skin bacteria into free fatty acids, some of which have antibacterial effects. Squalene makes up around 12% of sebum, and it acts as a powerful antioxidant. Unfortunately, it easily oxidizes into comedogenic squalene peroxide when exposed to air. Some other antioxidants in sebum are Coenzyme Q10 and Vitamin E. Other components like wax esters and fatty acids contribute to the skin barrier.

Does sebum clog pores?

While sebum is important for skin health, excess oil production can lead to clogged pores and acne breakouts. A key component of sebum is squalene, which oxidizes when exposed to air. The oxidation product, known as squalene peroxide, is comedogenic and can clog pores. Clogged pores combined with acne-causing bacteria can trigger the inflammatory breakouts associated with acne. Those with excess sebum production or “very oily skin” are at greatest risk for pore-clogging and acne breakouts.

sebum and your diet

Does your diet change your sebum?

Research shows that diet impacts sebum production. For example, high sugar diets have been associated with increased sebum secretion. One study found that males who consumed low glycemic diets had changes in their sebum fatty acid composition. Other research suggests that components of Western diets, like palmitic acid from dairy and meat, may activate inflammatory pathways linked to acne. While more studies are needed, it appears that sticking to a low sugar diet with less dairy and meat may help reduce excessive sebum production.

Sebum and the microbiome

The mixture of microbes living on the skin is known as the skin microbiome. The makeup of sebum directly impacts which bacteria can grow. Sebum provides a food source for certain microbes, like Cutibacterium acnes, which digest various fats. C. acnes releases inflammatory free fatty acids that contribute to acne. On the other hand, sebum’s fatty acids have antibacterial effects against C. acnes and other microbes. The effect your sebum will have on your face's microbiome depends on factors like your skin type, your diet, and your lifestyle.

Stress and sebum production

Stress hormones are known to stimulate sebum production. For example, corticotropin-releasing hormone (CRH) binds to receptors on sebaceous glands and increases sebum secretion. CRH also ramps up conversion of precursor molecules into testosterone, which may further drive increased oil production. Other stress-associated molecules can also directly enhance sebum secretion. This helps explain why stress often triggers oily skin and acne flares. Using stress management techniques may help control stress-induced Sebum production.

Antioxidants in sebum

Antioxidants in sebum

In addition to its protective moisturizing properties, sebum contains antioxidants that defend against oxidative damage from free radicals. The main antioxidant present is vitamin E. Vitamin E is fat-soluble, so sebum provides a perfect delivery system to transport it to the skin’s surface. Other antioxidants like coenzyme Q10 are also found in sebum. These antioxidants protect the skin from oxidative stress and UV radiation.

Sebum and skin cancer

While sebum mainly guards against dryness, it may also protect from skin cancer development in some cases. Areas of skin with minimal sebaceous glands, like the lips, are prone to dryness and have a higher risk of certain skin cancers. On the other hand, when sebum oxidizes on the skin it can itself create free radicals, this is one of the reasons it is important to wash your face when it has been greasy for a while.

Why do you need to wash sebum off your face?

While a thin film of sebum might protect you during the day, excess oil can cause breakouts and a greasy appearance. Sebum, sweat, dead skin cells, and environmental pollutants can combine to clog pores and create a breeding ground for acne-causing bacteria. That’s why it is recommended to wash your face twice a day – this removes excess sebum, debris, and germs from the skin’s surface. Using a cleanser that compliments the skin’s natural pH is ideal. Here are some great antibacterial and salicylic acid cleansers:

Is sebum occlusive?

Sebum prevents water evaporation from the skin’s surface, but is not as occlusive as petroleum-based ingredients. However, it does provide occlusive properties that reduce water loss. Even though it is not completely occlusive, a film of sebum on the skin’s surface slows down evaporation and provides moisturizing effects. Those with very oily skin types rarely suffer from dryness because their sebum production creates an occlusive layer that locks in hydration. If you have combination skin, you might only have oily skin sometimes.

Non-comedogenic skin care for oily skin

If your skin is oily and you don't want to include any comedogenic ingredients in your skin care routine, I have recommendations for you! This collection of non-comedogenic skin care products was curated specifically for acne-prone and oily skin types that need to closely regulate the sebum on their skin.

Make sure to take the Baumann Skin Type Quiz to only buy the best products for your skin today!

Level up your skin care knowledge with medical advice from dermatologists

Best References and Scientific Publications on Sebum and the Sebaceous glands

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2. Passi S, De Pità O, Puddu P, Littarru GP. Lipophilic antioxidants in human sebum and aging. Free Radic Res. 2002;36(4):471-7.

3. Strauss J, Downing FJ, Ebling ME, Stewart ME. Sebaceous glands. In: Physiology Biochemistry and Molecular Biology of the Skin, Goldsmith LA, ed. New York, NY: Oxford University Press, 1991, pp. 712-740.

4. Cunliffe WJ, Burton JL, Shuster S. The effect of local temperature variations on the sebum excretion rate. Br J Dermatol. 1970;83(6):650-4.

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6. Nouveau-Richard S, Zhu W, Li YH, Zhang YZ, Yang FZ, Yang ZL, et al. Oily skin: specific features in Chinese women. Skin Res Technol. 2007;13(1):43-8.

7. Clarke SB, Nelson AM, George RE, Thiboutot DM. Pharmacologic modulation of sebaceous gland activity: mechanisms and clinical applications. Dermatol Clin. 2007;25(2):137-46, v.

8. Segot-Chicq E, Compan-Zaouati D, Wolkenstein P, Consoli S, Rodary C, Delvigne V, et al. Development and validation of a questionnaire to evaluate how a cosmetic product for oily skin is able to improve well-being in women. J Eur Acad Dermatol Venereol. 2007;21(9):1181-6.

9. Thiboutot D. Regulation of human sebaceous glands. J Invest Dermatol. 2004;123(1):1-12.

10. Piérard GE, Piérard-Franchimont C, Lê T, Lapière C. Patterns of follicular sebum excretion rate during lifetime. Arch Dermatol Res. 1987;279 Suppl:S104-7.

11. Daniel F. The seborrheic skin. Rev Prat. 1985;35(53):3215-24.

12. Lasek RJ, Chren MM. Acne vulgaris and the quality of life of adult dermatology patients. Arch Dermatol. 1998;134(4):454-8.

13. Roh M, Han M, Kim D, Chung K. Sebum output as a factor contributing to the size of facial pores. Br J Dermatol. 2006;155(5):890-4.

14. Pham DM, Boussouira B, Moyal D, Nguyen QL. Oxidization of squalene, a human skin lipid: a new and reliable marker of environmental pollution studies. Int J Cosmet Sci. 2015;37(4):357-65.

15. Lovászi M, Szegedi A, Zouboulis CC, Törőcsik D. Sebaceous-immunobiology is orchestrated by sebum lipids. Dermatoendocrinol. 2017;9(1):e1375636.

16. De Luca C, Valacchi G. Surface lipids as multifunctional mediators of skin responses to environmental stimuli. Mediators Inflamm. 2010;2010:321494.

17. Akaza N, Akamatsu H, Numata S, Matsusue M, Mashima Y, Miyawaki M, et al. Fatty acid compositions of triglycerides and free fatty acids in sebum depend on amount of triglycerides, and do not differ in presence or absence of acne vulgaris. J Dermatol. 2014;41(12):1069-76.

18. Katsuta Y, Iida T, Inomata S, Denda M. Unsaturated fatty acids induce calcium influx into keratinocytes and cause abnormal differentiation of epidermis. J Invest Dermatol. 2005;124(5):1008-13.

19. Yamamoto A, Serizawa S, Ito M, Sato Y. Effect of aging on sebaceous gland activity and on the fatty acid composition of wax esters. J Invest Dermatol. 198;89(5):507-12.

20. Smith RN, Braue A, Varigos GA, Mann NJ. The effect of a low glycemic load diet on acne vulgaris and the fatty acid composition of skin surface triglycerides. J Dermatol Sci. 200;50(1):41-52.

21. Ge L, Gordon JS, Hsuan C, Stenn K, Prouty SM. Identification of the delta-6 desaturase of human sebaceous glands: expression and enzyme activity. J Invest Dermatol. 2003;120(5):707-14.

22. Snodgrass RG, Huang S, Choi IW, Rutledge JC, Hwang DH. Inflammasome-mediated secretion of IL-1β in human monocytes through TLR2 activation; modulation by dietary fatty acids. J Immunol. 201;191(8):4337-47.

23. Nakatsuji T, Kao MC, Zhang L, Zouboulis CC, Gallo RL, Huang CM. Sebum free fatty acids enhance the innate immune defense of human sebocytes by upregulating beta-defensin-2 expression. J Invest Dermatol. 2010;130(4):985-94.

24. Rawlings AV. Ethnic skin types: are there differences in skin structure and function? Int J Cosmet Sci. 2006;28(2):79-93.

25. Jacobsen E, Billings JK, Frantz RA, Kinney CK, Stewart ME, Downing DT. Age-related changes in sebaceous wax ester secretion rates in men and women. J Invest Dermatol. 1985;85(5):483-5.

26. Chiba K, Yoshizawa K, Makino I, Kawakami K, Onoue M. Comedogenicity of squalene monohydroperoxide in the skin after topical application. J Toxicol Sci. 2000;25(2):77-83.

27. Chiba K, Kawakami K, Sone T, Onoue M. Characteristics of skin wrinkling and dermal changes induced by repeated application of squalene monohydroperoxide to hairless mouse skin. Skin Pharmacol Appl Skin Physiol. 2003;16(4):242-51.

28. Chiba K, Sone T, Kawakami K, Onoue M. Skin roughness and wrinkle formation induced by repeated application of squalene-monohydroperoxide to the hairless mouse. Exp Dermatol. 1999;8(6):471-9.

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34. Zouboulis CC. Human skin: an independent peripheral endocrine organ. Horm Res. 2000;54(5-6):230-42.

35. Fritsch M, Orfanos CE, Zouboulis CC. Sebocytes are the key regulators of androgen homeostasis in human skin. J Invest Dermatol. 2001;116(5):793-800.

36. Thiboutot D, Jabara S, McAllister JM, Sivarajah A, Gilliland K, Cong Z, et al. Human skin is a steroidogenic tissue: steroidogenic enzymes and cofactors are expressed in epidermis, normal sebocytes, and an immortalized sebocyte cell line (SEB-1). J Invest Dermatol. 2003;120(6):905-14.

37. Zouboulis CC, Seltmann H, Hiroi N, Chen W, Young M, Oeff M, et al. Corticotropin-releasing hormone: an autocrine hormone that promotes lipogenesis in human sebocytes. Proc Natl Acad Sci U S A. 2002;99(10):7148-53.

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39. Zouboulis CC. Is acne vulgaris a genuine inflammatory disease? Dermatology. 2001;203(4):277-9.

40. Böhm M, Schiller M, Ständer S, Seltmann H, Li Z, Brzoska T, et al. Evidence for expression of melanocortin-1 receptor in human sebocytes in vitro and in situ. J Invest Dermatol. 2002;118(3):533-9.

41. Passi S, Picardo M, Morrone A, De Luca C, Ippolito F. Skin surface lipids in HIV sero-positive and HIV sero-negative patients affected with seborrheic dermatitis. J Dermatol Sci. 1991;2(2):84-91.

42. Picardo M, Passi S, De Luca C, Morrone A, Bartoli F, Ippolito F. Skin surface lipids in patients affected with atopic dermatitis. In: Immunological and Pharmacological Aspects of Atopic and Contact Eczema. Vol. 4. Czernielewski JM, ed. Basel: Karger, 1991, pp. 173-174.

43. Benfenati A, Brillanti F. Sulla distribuzione delle ghiandole sebacee nella cute del corpo umano. Arch Ital Dermatol. 1939;15:33-42.

44. Powell EW, Beveridge GW. Sebum excretion and sebum composition in adolescent men with and without acne vulgaris. Br J Dermatol. 1970;82(3):243-9.

45. Cunliffe WJ, Forster RA, Williams M. A surface microscope for clinical and laboratory use. Br J Dermatol. 1974;90(6):619-22.

46. Tosti A. A comparison of the histodynamics of sebaceous glands and epidermis in man: a microanatomic and morphometric study. J Invest Dermatol. 1974;62(3):147-52.

47. Jenkinson DM, Elder HY, Montgomery I, Moss VA. Comparative studies of the ultrastructure of the sebaceous gland. Tissue Cell. 1985;17(5):683-98.

48. Rajaratnam RA, Gylling H, Miettinen TA. Serum squalene in postmenopausal women without and with coronary artery disease. Atherosclerosis. 1999;146(1):61-4.

49. Pochi PE, Strauss JS, Downing DT. Age-related changes in sebaceous gland activity. J Invest Dermatol. 1979;73(1):108-11.

50. Stewart ME, Downing DT. Proportions of various straight and branched fatty acid chain types in the sebaceous wax esters of young children. J Invest Dermatol. 1985;84(6):501-3.

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52. Baumann, L. Ch. Cosmeceuticals and cosmetic Ingredients (McGraw Hill 2015)