Pores Don't Open and Close — So What Actually Affects Them?

“Open your pores with hot steam, then close them with cold water” — this advice has been passed down for generations. The problem is that pores have no mechanism for opening and closing. They have no muscles, no valves and no structure that would allow them to contract and dilate on demand.

The anatomy of pores — why they can't “open”

What we casually call “pores” are the openings of hair follicles and sebaceous glands at the surface of the skin. Each pore is the opening of a canal that leads down to a hair follicle with its attached sebaceous (oil) glands.

The key fact: pores have no sphincter muscle and no muscle tissue of any kind that could actively narrow or widen them. Unlike the pupil of the eye (which has a constrictor and a dilator muscle) or blood vessels (which have a layer of smooth muscle), pores are static openings in the epidermis.

Their size depends on factors we can't fully control:

• Genetics: the single biggest factor determining pore size.
• Sebum production: excess oil widens the canal and enlarges the visible pore.
• Age: the loss of collagen and elastin causes the skin to “sag” around the pores, making them look larger.
• Photoaging: UV radiation degrades the collagen surrounding the pores (Youn et al., 2005, Journal of Dermatological Science).

So what does hot steam actually do?

Hot steam doesn't “open” pores — but that doesn't make it useless. Heat and moisture cause:

• Softening of sebum: oil (skin grease) becomes more fluid when warmed, which makes it easier to remove from the pores.
• Dilation of blood vessels: heat improves microcirculation in the skin, which can create the impression of “open” pores (redness, slight swelling).
• Hydration of the epidermis: steam moisturizes the stratum corneum, which temporarily smooths the texture.

The effect is temporary and concerns the softness of the sebum, not the size of the pores. That's why steaming the face before extracting blackheads makes them easier to remove — not because the pore has “opened,” but because the contents of the pore have become more fluid.

And cold water?

Cold water doesn't “close” pores (there's nothing to close), but it does cause a temporary constriction of the blood vessels (vasoconstriction). The skin looks smoother and more taut and the pores appear less visible — but the effect lasts minutes to an hour and is purely cosmetic.

Rinsing your face with cold water after cleansing won't do any harm (unless you have rosacea, where sudden temperature changes can make things worse), but it does not permanently reduce pore size.

Ingredients that genuinely reduce the appearance of pores

Niacinamide (vitamin B3) — 2–5%

Niacinamide is one of the best-researched ingredients when it comes to pores. A study by Draelos et al. (2006) in Cutis showed that 5% niacinamide used for 12 weeks significantly reduced the appearance of pores. The mechanism:

• Regulating sebum production: less sebum = a less dilated oil canal = a smaller visible pore.
• Improving the skin barrier: niacinamide boosts ceramide production, which improves the overall texture of the skin.
• Anti-inflammatory action: less inflammation = less redness and swelling around the pores.

Salicylic acid (BHA) — 1–2%

Salicylic acid is lipophilic (it dissolves in fats), which means it penetrates inside the pores and dissolves the sebum that forms blackheads. Regular use of a BHA:

• Clears the pores of excess sebum and dead cells.
• Prevents the formation of open and closed comedones.
• Visually reduces the appearance of pores (clean pores look smaller).

A study by Grimes et al. (2004) confirmed the effectiveness of 2% salicylic acid in reducing pore size and improving skin texture after 12 weeks of use.

Retinol and retinoids

Retinol speeds up cell turnover and stimulates collagen synthesis. Thicker, healthier skin around the pores makes the pores look smaller. The effect takes 3–6 months of regular use. Check out retinol products in the PurScore ingredient database.

A practical plan for reducing the appearance of pores

1. Cleanse morning and evening: clean skin = a lower risk of clogged pores.
2. BHA 1–2% in the evening, 2–3 times a week: dissolves sebum inside the pores.
3. Niacinamide 2–5% in the morning and/or evening: regulates sebum and improves texture.
4. SPF every day: protects the collagen around the pores from UV degradation.
5. Retinol in the evening (optional): stimulates collagen and improves skin structure.

Don't introduce all the products at once — start with a BHA, add niacinamide after 2–3 weeks, and only bring in retinol once your skin has adapted to the earlier ingredients.

In summary

Pores don't open or close — they have no physical way of doing so. Hot steam softens sebum (useful before cleansing), and cold water gives a short-lived tightening effect. To permanently reduce the appearance of pores (not their size — that's largely genetic), reach for niacinamide, salicylic acid and sun protection.

Want to find products with the right ingredients? Use the PurScore search tool and check whether your toner or serum really contains an effective concentration of BHA or niacinamide.