Oily skin comes from oil glands that respond to hormones, genetics and heat, and pores are tiny dips where those glands open, so their size is largely set by your genes, age and skin structure. No product makes pores permanently smaller, but niacinamide, a BHA and a light routine can visibly reduce shine and help pores look less noticeable.
Oil glands sit inside every hair follicle on the face, and androgen hormones can turn up their output [1]. How oily you are also depends on genetics, which part of the face you look at, and the weather.
Pores aren't little doors that open and close. A large five-country imaging study of 2,585 women described visible pores as slight dips in the skin surface where many oil and sweat glands open [2]. Pore size and number varied widely between countries and levelled off after about 40, and the authors noted that oil output alone didn't explain who had the most visible pores [2]. The study was funded by a cosmetics company, so read it as a large description rather than the final word.
Heat and humidity make shine feel worse, and a Victorian dermatologist notes that breakouts can flare moving from dry to humid conditions [8]. Heavy creams in hot weather can also trap sweat and oil; together with heat and occlusive products, that is a recognised trigger for fungal acne lookalikes [9].
Over-cleaning backfires. Alcohol-based or oil-based cleansers and scrubbing irritate skin, and dermatologists still recommend moisturising oily skin after cleansing [3].
When to see a doctor
Oily skin isn't a medical problem on its own, but see your GP if it comes with persistent or painful breakouts, or breakouts that are leaving marks [1].See your GP for itchy, same-sized bumps on the chest, back or hairline, which may be fungal acne rather than oiliness [9].Talk to your GP if your skin changes suddenly alongside other changes in your body that you can't explain.A pharmacist can help if breakouts come with the shine; see our acne-prone skin page for pharmacy options.
No product makes pores permanently smaller. Their size is mostly set by genetics, age and skin structure, but less oil and smoother skin can make them look smaller [2][4].
General information only, not medical advice.