Why Do Some People Have Oilier Skin than Others?
A Number of Factors, Predominantly Hormones, Are to Blame
- Properties of Sebum and Sebaceous Glands
- Factors in the Body That Control Sebum Production
- Hormone Levels Differ in Individuals with and Without Oily Skin
- Diet May Also Affect Sebum Production
Oily skin, also called seborrhea, is a condition marked by increased sebum (skin oil) production. Sebaceous glands are small, mostly microscopic glands attached to hair follicles that release sebum into skin pores. This sebum then drains out of the pores and onto the skin's surface. The face, scalp, and upper torso contain the most sebaceous glands, and therefore are most likely to experience the side effects of excess sebum production, which include enlargement of pores, and a shiny, greasy skin appearance. Although not a disease, people with seborrhea are more prone to develop diseases like acne and seborrheic dermatitis, a disease that causes red, scaly patches on the body.
Properties of Sebum and Sebaceous Glands
Sebum is made of a variety of lipids. Lipids are molecules with an oily feel, but which are not always oils. These lipids include squalene, cholesterol, cholesterol esters, triglycerides, and important lipids called wax esters, which are not found anywhere else in the human body, but make up 25% of sebum. When sebum is released from the hair follicle, certain bacterial enzymes break down the triglyceride component of sebum into lipids called free fatty acids, as well as into smaller triglycerides called mono- and diglycerides, while retaining the original lipids. Sebum serves several purposes for the skin.
- It protects the skin by lubricating it, which reduces water loss and shields the skin from damage.
- It possesses antibacterial properties, which defend the skin from infections.
- It contains antioxidants, which counteract the effect of harmful chemicals.
- It protects the skin from harmful rays found in sunlight.
- It can help to regulate inflammation.
- It aids in the wound healing process of the skin.
Sebum is produced deep within the skin in sebaceous glands. Sebaceous glands are present nearly everywhere on the body, except on the palms of the hands and soles of the feet. Each sebaceous gland contains two types of cells: peripheral sebocytes and central sebocytes. Initial peripheral sebocytes are flat, immature cells located toward the edges of a sebaceous gland that do not produce lipids of sebum. However, as peripheral sebocytes mature and divide, they begin producing lipids. Eventually, the peripheral sebocytes move to the center of the sebaceous gland, maturing into central sebocytes. At this point they produce a large amount of lipids, and disintegrate, releasing their lipids into the skin pore.1-3
Factors in the Body That Control Sebum Production
Sebum production is stimulated by endogenous (in the body) factors, such as hormones, and exogenous (out of the body) factors, including diet. In order to understand why some people have oilier skin than others, we must first examine how the body normally controls the production of sebum. Scientists have identified four main factors found within the body that regulate sebum production.
Androgens increase sebum production
Androgens are male sex hormones that are found in both males and females. Testosterone is the most commonly studied androgen. The majority of testosterone present in the body is produced in the gonads and adrenal glands, which are found above the kidneys. However, testosterone can also be produced in the sebaceous glands. When testosterone enters a sebum-producing cell, called a sebocyte, it is converted into a molecule called 5α-hydydrosterone (DHT). DHT can then regulate cellular specialization, increase cellular growth and division, and most importantly for those with oily skin, increase the production of lipids. Scientists do not know whether androgens like testosterone must be produced in the skin, in the adrenal glands, or in both in order to cause an increase in sebum production. However, researchers have speculated that people with oilier skin are likely more sensitive to androgens in general. Several studies support this idea and have found that androgens are directly related to increases in sebum production, and therefore oilier skin.2
Expand to read details of studies
A 1969 study published in the Journal of Investigative Dermatology studied the effect of testosterone on the sebaceous glands in men. To perform this study, the researchers injected testosterone into 27 adult males on a weekly basis and then measured changes in sebum production and sebaceous gland size over the course of 11 weeks. The researchers found that the testosterone injections increased both the amount of sebum produced and the size of the sebaceous gland, so they concluded that increases in testosterone can increase sebum production and likely also increase oily skin.4
Two 1983 studies published in the New England Journal of Medicine and the Journal of Investigative Dermatology studied the levels of androgens in women with acne. Both studies found that women with acne have higher androgen levels than women without acne. Therefore, the researchers concluded that acne was correlated with an excess of androgens. The researchers involved with this study did not report on whether the elevated androgen levels also caused oily skin. However, as acne is often correlated with oily skin, it is likely that women with acne and excess androgens also had oilier skin.5,6
A 1993 study published in the Journal of Endocrinology and Metabolism studied sebum production in men without androgens in order to determine if androgens likely controlled the production of sebum. The men without androgens in this study were pseudohermaphrodites, who are unable to produce proper sex hormones. The researchers found that the pseudohermaphrodites studied lacked androgens and that because of this, they also did not produce sebum. Therefore, the researchers concluded that there was "absolute androgen control of sebum production."7
A 1994 study published in the Archives of Dermatology examined the hormones of young girls with acne who had not yet undergone puberty. Prepubescent girls often do not have the same levels of androgens as girls who have gone through puberty, so the point of this study was to understand if the girls' prepubescent acne was due to abnormal androgen levels. This study examined the hormone levels of 623 acne-prone young girls with an average age of 10 years. They found that one androgen called dehydroepiandrosterone (DHEA) was present at abnormally high levels in the prepubescent girls with acne. DHEA is a hormone that is required for testosterone synthesis. Therefore, the researchers concluded that the prepubescent girls' acne was likely caused by an elevated level of the androgen DHEA in their blood since androgens, including testosterone, stimulate sebum production. The researchers involved in this study did not report on whether the increase in DHEA also caused oilier skin. However, as acne is often correlated with oily skin, it is likely that the prepubescent girls with acne and elevated DHEA levels also had oilier skin.2,8
Growth hormones increase sebum production
Growth hormones are hormones secreted by the pituitary gland that stimulate the body to produce insulin-like growth factor 1 (IGF-1). Scientists believe that IGF-1 is involved in acne development and sebum production because people show the highest levels of IGF-1 during adolescence, which is also when people are most likely to experience acne. One study examining the connection between IGF-1 and sebum production found that acne patients had increased levels of IGF-1 and increased sebum secretion. Another study found that IGF-1 can promote the synthesis of lipids in sebocytes. These studies, combined with other clinical evidence showing that growth hormone disorders are associated with abnormal sebum levels and acne, have led researchers to believe that IGF-1 levels are directly correlated with sebum production. Therefore, oily skin may in part be caused by increased IGF-1 levels in the skin.1
Estrogens suppress sebum production
Estrogens are female sex hormones that are found in both males and females. Women often take estrogen in the form of birth control pills to suppress ovulation. Estrogen also works to suppress sebum production, although a much higher dose of estrogen is required to suppress sebum production than what is required for ovulation suppression. In order to suppress the production of sebum, estrogen works in a manner that scientists have not yet identified. However, researchers have proposed three hypotheses to explain how estrogens might reduce sebum production. These include directly counteracting the effects of androgens, inhibiting the production of testosterone, or controlling the activation of genes responsible for synthesizing lipids. Regardless, estrogens work to reduce sebum production, and therefore different levels of estrogen may partly explain why some people's skin is oilier than others'. More research will need to be performed to confirm how estrogen suppresses sebum production and if estrogen is indeed a cause of less-oily skin.9
Neuropeptides regulate sebum production
Neuropeptides are small proteins found within nerve cells and help to regulate a variety of bodily functions, including sebum production. Researchers have found that sebocytes can respond to different neuropeptides that regulate sebum production. Depending on the neuropeptide the sebocyte encounters, it may activate or suppress sebum production.3 Therefore, differences in how sebocytes and the sebaceous glands respond to neuropeptides may also partly explain why some people have oilier skin than others.
Hormone Levels Differ in Individuals with and Without Oily Skin
As oily skin is not a disease, scientists have not performed studies comparing the differences between people with and without oily skin. However, researchers have investigated differences between people with and without acne. As oily skin is often associated with acne, scientists can use these studies to infer what differences may exist between people with and without oily skin. Four main studies have been performed to identify what hormonal difference may exist between acne sufferers and individuals without acne. As sebum production is regulated through various hormones, the conclusions drawn in these studies likely offer explanations of why some people have oilier skin than others.
Expand to read details of studies
A 1983 study published in The Journal of Investigative Dermatology investigated the levels of androgens in adult females with and without acne. The researchers found that 52% of adult acne patients showed "at least one abnormal hormone level" compared to patients without acne. They also found that androgens like testosterone and DHEA were elevated.9 Therefore, it is likely that women with elevated levels of androgens are also likely to have oilier skin.
A 1999 study published in the Archives of Dermatology investigated the levels of androgens and IGF-1 in both adult male and female patients with and without acne. The researchers found that androgen levels were increased in both male and female acne patients, while IGF-1 levels were similar in acne and non-acne patients. This study also examined the activities of androgen-producing proteins called 17β-hydroxysteroid dehydrogenase and 5α-reductase. These two proteins are enzymes and metabolize (work to break down) testosterone into DHT, which is a more potent, active form. However, no differences in enzyme activities were found between individuals with and without acne. Therefore, the scientists concluded that the main difference between individuals with and without acne was the levels of androgens, and that acne patients were more likely to have higher levels of androgens. Although oily skin was not a focus of this study, elevated androgen levels will likely also cause increases in sebum production and oilier skin.10,11
A 2008 study published in the British Journal of Dermatology investigated the amount of sebum and IGF-1 levels in 11 male and 5 female acne patients. The researchers found that higher sebum levels were correlated with increased IGF-1 levels in men and women. However, an increase in IGF-1 levels was associated with higher acne lesion counts in women, but not men.12 Therefore, the researchers concluded that IGF-1 played an important role in sebum production, but not necessarily acne, in both men and women.
From all these studies, it can be concluded that the majority of people with increased sebum secretion disorders usually have elevated androgen and IGF-1 levels compared to healthy individuals. However, this does not necessarily cause acne, as there are also acne patients with normal serum (a component of blood) levels of these hormones. Based on this data, scientists speculate that androgens produced in the skin and elsewhere in the body influence sebum production. We were unable to find any study which compares estrogen levels in women with seborrhea or acne with those of healthy individuals. As for other factors which influence sebum production, such as neuropeptides, or specific receptor types, no study compared these factors in persons with seborrheic disorders with those in healthy individuals. For now, it seems that oily skin, and disorders associated with it, is mainly a consequence of increased androgen production and IGF-1 levels.
Diet May Also Affect Sebum Production
Research has identified that dietary choices may impact the amount of sebum produced in the skin. Studies have found that two specific diets may decrease sebum production in the skin. The first diet is a low glycemic load diet, which is a diet that prohibits the consumption of simple carbohydrates, such as sugars, found in foods like candy, white bread, and soda. Research has found that a low-glycemic diet may cause a reduction in the amount of sebum produced. A typical Western diet contains many sugary foods, which may cause increases in IGF-1 levels, "promoting the development of acne."3 The second diet is an extreme caloric restriction diet, also known as fasting. Two studies have found that fasting can reduce sebum production by up to 20% in the short term. The decrease in sebum production caused by fasting is reversed when the individual returns to a normal diet. Therefore, diet can influence sebum production and may partly explain why some people have oilier skin than others.3
Oily skin, also called seborrhea, is due to the overproduction of sebum (skin oil), which causes enlarged skin pores and a greasy skin appearance. Although not a disease in itself, oily skin predisposes people to develop acne. Normally, sebum is an important component for skin health, as it protects the skin. However, several factors trigger an increase in sebum. Hormones are the most prevalent of these factors. However, external factors, such as a high-glycemic diet may also cause an increase in sebum production. Although no studies have examined differences between people with and without oily skin, studies involving people with and without acne have found that hormones, specifically androgens, are more likely to be associated with acne and oilier skin. However, more research is needed to identify how other hormones and factors like diet may also lead to oilier skin.
- Smith, K. R. & Thiboutot, D. M. Sebaceous gland lipids: friend or foe? J Lipid Res 49, 271 - 281 (2008).
- Thibutout, D. Regulation of Human Sebaceous Glands. J Invest Dermatol 123, 1 - 12 (2004).
- Makrantonaki, E., Ganceviciene, R. & Zouboulis, C. C. An update on the role of the sebaceous gland in the pathogenesis of acne. Dermatoendocrinol 3, 41 - 49 (2011).
- Pochi, P. E. & Stauss, J. S. Sebaceous Gland Response in Man to the Administration of Testosterone, ∆4-Androstenedione, and Dehydroisoandrosterone. J Investig Dermatol 52, 32 - 36 (1969).
- Marynick, S. P., Chakmakjian, Z. H., McCaffree, D. L. & Herndon, J. H. Androgen Excess in Cystic Acne. New Engl J Med 308, 981 - 986 (1983).
- Lucky, A. W., McGuire, J., Rosenfield, R. L., Lucky, P. A. & Rich, B. H. Plasma Androgens in Women with Acne Vulgaris. 81, 70 - 74 (1983).
- Imperato-McGinley, J. et al. The androgen control of sebum production. Studies of subjects with dihydrotestosterone deficiency and complete androgen insensitivity. J Clin Endocrinol Metab 76, 524 - 528 (1993).
- Lucky, A. W. et al. Acne vulgaris in premenarchal girls. An early sign of puberty associated with rising levels of dehydroepiandrosterone. Arch Dermatol 130, 308 - 314 (1994).
- Lucky, A. W., McGuire, J., Rosenfield, R. L., Lucky, P. A. & Rich, B. H. Plasma androgens in women with acne vulgaris. J Investig Dermatol 81, 70 - 74 (1983).
- Thiboutot, D., Gilliland, K. & Lookingbill, D. Androgen metabolism in sebaceous glands from subjects with and without acne. Arch Dermatol 135, 1041 - 1045 (1999).
- Cappel, M., Mauger, D. & Thiboutot, D. Correlation Between Serum Levels of Insulin-like Growth Factor 1, Dehydroepiandrosterone Sulfate, and Dihydrotestosterone and Acne Lesion Counts in Adult Women. Arch Dermatol 141, 333 - 338 (2005).