A 60-person imaging study tied pore size most strongly to sebum output, while a million-person dataset added age, sex and climate patterns. Here is what that means for a realistic routine, and what a 2% niacinamide trial did and did not measure.
· 5 min read
Pore size is one of the most searched skin concerns, and it attracts some of the loudest claims. Products promise to shrink, close or erase pores. The published research is more modest and more useful: it points to a short list of factors that seem to change how pores look, and a few that are mostly fixed.
A facial pore is the surface opening of a hair follicle and its attached oil gland. You cannot open or close it, because there is no muscle or lid. What you see is the diameter of that opening and the shadow it casts, which is why pores look larger under bright overhead light and smaller in soft, even light. Any honest goal is therefore about the appearance of pores, not their literal size.
The most cited controlled measurement comes from a 2006 study in the British Journal of Dermatology. Researchers recruited 60 volunteers, 30 men and 30 women, photographed their pores with a dermoscopic video camera, measured pore size with image-analysis software, and measured sebum output with a Sebumeter. Higher sebum output was the factor most strongly correlated with larger pores. The relationship was moderate rather than absolute: the correlation was r = 0.47 in men and r = 0.38 in women, which the authors read as a sign that other factors also matter, particularly in women.
Two other findings in the same work are worth knowing. Male sex and older age were each independently associated with larger pores. And the study did not find that blemish severity was significantly associated with pore size. In plain terms, having visible pores does not mean your skin is congested, and a clear complexion can still have large-looking pores.
A 2024 analysis scored cheek, nose and other pore areas from selfie images of 1,000,568 app users in China aged 16 to 60, using an AI model that agreed closely with dermatologist grading on a 70-image check. Men had more severe pore scores than women in every facial area, with the gap largest on the nose at 26 percent and smallest on the cheek at 4 percent. Among women, cheek pore scores rose until about age 26, held steady near 30, and then rose again between 40 and 44.
These numbers describe populations, not you. The study is cross-sectional, participants were self-selected app users, and the work was funded by Estée Lauder with company employees among the authors. It is a useful map of patterns, not a forecast for any one person.
The same dataset compared city-level environmental data with cheek pore scores. Lower relative humidity was associated with higher scores, with each 1 percent drop in humidity linked to a 0.6 percent rise in the cheek score. Higher surface solar radiation was also associated with higher scores, about a 0.48 percent rise per 1 percent increase in radiation. Air pollution measures showed low to moderate correlations that were not statistically significant.
Two cautions apply. These are city averages matched to individual faces, so they cannot show cause. And the sun measure was surface solar radiation, not UV specifically. Still, the pattern lines up with ordinary sun-protection advice: daily sunscreen is a reasonable habit if pore appearance matters to you, though this study cannot say it will change anything.
Niacinamide is the ingredient most often tied to pore claims, so it is worth reading what the key trial actually tested. In a 2006 study published in the Journal of Cosmetic and Laser Therapy, 100 Japanese volunteers used either a 2 percent niacinamide moisturizer or a placebo moisturizer for 4 weeks, with sebum excretion rate measured at baseline, week 2 and week 4. The niacinamide group showed significantly lower sebum excretion rate at weeks 2 and 4 compared with the start.
A separate 30-person split-face study in Caucasian volunteers ran 6 weeks. There, casual sebum level was significantly reduced, but sebum excretion rate was not. The authors concluded that 2 percent niacinamide may be effective in lowering sebum excretion rate in Japanese individuals and casual sebum level in Caucasian individuals.
Notice what is missing from the abstract: pore size. The trial measured oil, not pore dimensions. Because oil output is the strongest measured correlate of pore size in the earlier study, it is a reasonable idea that less surface oil could make pores look less prominent, but that is an inference, not something these papers demonstrated together. Sample sizes were also small, and the sponsor details are not stated in the abstract, so read the full paper if you plan to rely on it.
Putting the evidence together, a plan can be built around what has support and what is plausible.
The best-supported idea is that oil output tracks pore size more than any other measured factor, while age, sex and hormonal timing also play roles you cannot change. Niacinamide at 2 percent has controlled data on sebum, not on pores. If pore appearance bothers you, aim for steady oil management, daily sun protection and consistent photos, and treat any product that promises to close or shrink pores with skepticism. If you have questions about a specific concern, talk to a dermatologist.
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