What are the causes of pore dilation?

The correlation between excessive sebum production and pore dilation is well documented. The higher the sebum secretion, the more pores tend to appear enlarged. Sebum, produced by the sebaceous glands, functions to hydrate and protect the skin. However, when produced in excess, it accumulates on the surface and within hair follicles, which causes a mechanical enlargement of skin pores.

In women, this phenomenon can fluctuate over the course of the menstrual cycle. Studies have shown that during ovulation, sebum production as well as pore size are significantly increased. This hormonal variation is partly explained by the rise in luteinizing hormone (LH) and follicle-stimulating hormone (FSH), as well as by the gradual increase in progesterone at this point in the cycle. The estrogen, at physiological doses, exerts little effect on sebaceous gland regulation. It is therefore likely the combination of LH, FSH, and progesterone that stimulates their activity.

Another key player is Insulin-like Growth Factor-1 (IGF-1), a hormone involved in cellular growth and metabolism. IGF-1 stimulates sebaceous gland lipogenesis via activation of the phosphoinositide 3-kinase/Akt pathway, thereby increasing sebum production. Several scientific studies have established a positive correlation between serum IGF-1 levels, facial sebum excretion, and pore size. Sensitivity to IGF-1 and the propensity to produce more sebum vary among individuals. Some genetic factors influence the density and activity of sebaceous glands, as well as the responsiveness of hormonal receptors. Thus, certain individuals, even with similar levels of IGF-1 or sex hormones, will develop greater sebum production and more visible pores than others.

Skin aging is a major factor in pore dilation, as it affects both the structure and elasticity of the skin. Enlarged pores are characterized by an irregular skin surface, an abnormal dermo-epidermal junction, and an altered extracellular matrix. For reference, the extracellular matrix is the network of proteins and polysaccharides that supports the dermal cells of the skin and ensures its elasticity and firmness. Researchers have demonstrated a pronounced undulation of the dermo-epidermal junction around pores, forming a stalagmite-like structure. This configuration, which resembles small vertical protrusions, is now recognized as a marker of enlarged pores and skin aging. A study conducted by KITAHARA and colleagues on 138 volunteers of various ages confirmed that the degradation of skin structure is closely linked to age and pore size.

Skin aging also leads to a loss of elasticity in the structures surrounding pores. For example, microfibril-associated glycoprotein-1 (MAGP-1), a protein essential for elastic fiber formation, decreases with age around hair follicles and pores, reducing skin tension and promoting their enlargement. The degradation of collagen, another protein critical for maintaining the extracellular matrix, also contributes to tissue sagging around pores.

Finally, a low-grade chronic inflammatory mechanism linked to aging, called inflammaging, could play a role in pore dilation. This silent inflammation is hard to detect but accumulates over time, causing internal skin damage. Over time, the complement system, part of the immune system, becomes persistently activated, leading to a buildup of pro-inflammatory cytokines and damaged macromolecules that the skin can no longer clear effectively. More specifically, complement system hyperactivation promotes monocyte differentiation into activated macrophages, which then release matrix metalloproteinases and reactive oxygen species that break down the extracellular matrix. In the case of enlarged pores, this chronic inflammation may contribute to the formation of stalagmite-like structures observed at the dermo-epidermal junction, thereby promoting pore widening.

Another important factor influencing the appearance of pores is the thickness of the hairs themselves. Indeed, pore size largely depends on the volume of the hair follicle, which is closely linked to that of the dermal papilla, a structure located at the base of the follicle. The dermal papilla plays a key role in hair growth: it is a highly vascularized region that delivers the nutrients and oxygen essential for hair growth. It contains cells and extracellular matrix whose number and volume directly influence the size of the mature hair follicle. The cells of the dermal papilla express androgen receptors, and androgen action is a major driver of follicle enlargement. Consequently, thicker or more voluminous hairs can visibly enlarge the pore on the skin’s surface.

Thus, pore appearance remains strongly influenced by hormonal and genetic factors. The sensitivity of dermal papillae to androgens varies among individuals, as do the density and structure of hair follicles, which explains why some people naturally exhibit more visible pores than others.

Chronic sun exposure is a major factor in skin aging and contributes to the appearance of enlarged pores. UV rays, particularly UVA, penetrate deep into the dermis and cause the degradation of collagen and elastin, which are responsible for skin elasticity and firmness. This loss of structural support around hair follicles leads to tissue laxity, making pores more visible. Moreover, UV rays promote the formation of free radicals that damage skin cells and the extracellular matrix. This alteration not only promotes a loss of skin tone but can also amplify the effects of inflammaging, which is already involved in the formation of stalagmite-like structures around pores.

Furthermore, sun exposure can increase sebum secretion. Indeed, in response to the sun’s drying effect, the sebaceous glands tend to react by boosting sebum production. Combined with reduced skin elasticity, this increase contributes to pore enlargement—particularly in facial areas most exposed to the sun, such as the forehead and nose. Finally, photo-induced damage accumulates over the years, which explains why pores tend to become more dilated with age, especially in individuals who are regularly exposed to sunlight without adequate protection. Prevention therefore relies on daily sun protection and the regular use of antioxidants.

Finally, a skincare routine can influence the appearance of pores. When it is not tailored to the skin type, it can accentuate their dilation and visibility. For example, the use of occlusive or overly rich products for a combination to oily skin promotes the accumulation of sebum and dead skin cells within hair follicles. This phenomenon leads to a progressive enlargement of the pore canal, giving the skin surface an uneven appearance.

Conversely, some overly aggressive regimens based on strong surfactants or excessively frequent exfoliation can damage the skin barrier. Once compromised, the skin responds by producing more sebum to compensate for the loss of its protective lipids, which encourages pore enlargement. Another bad habit: neglecting exfoliation. While over-exfoliating can weaken the skin, not exfoliating enough can result in a buildup of corneocytes that clog pores. That is why it is generally recommended to perform one to two exfoliations per week.

Find here our evidence-based tips for tightening dilated pores.

• CHUNG K. & al. Sebum output as a factor contributing to the size of facial pores. British Journal of Dermatology (2006).

• KITAHARA T. & al. Age-related changes in the epidermal architecture around facial pores. Journal of Dermatological Science (2008).

• TAKAHASHI K. & al. Analysis of the skin surface and internal structure around facial pores. Skin Research and Technology (2013).

• SEO S. J. & al. Facial pores: Definition, causes, and treatment options. Dermatologic Surgery (2015).

• CHEN Y. & al. Potential role of inflammaging mediated by the complement system in enlarged facial pores. Journal of Cosmetic Dermatology (2023).