Blackheads form when a pore gets clogged with a mix of oil and dead skin cells, and the surface of that plug darkens after being exposed to air. They’re one of the most common forms of acne, affecting roughly 85% of people between ages 12 and 24 at some point. Understanding what’s behind them starts with how your skin naturally produces oil and sheds cells, and why that process sometimes goes wrong.
How a Blackhead Forms
Your skin is covered in tiny hair follicles, each paired with an oil gland. These glands produce sebum, a waxy substance that keeps your skin moisturized and flexible. Normally, sebum travels up through the pore and spreads across the skin’s surface without any issues.
A blackhead starts when too much sebum gets produced, or when dead skin cells don’t shed properly and accumulate inside the pore. These two materials mix together and form a plug that partially blocks the opening. Unlike a whitehead, where the pore closes over completely, a blackhead stays open at the surface. That open top is what gives it its signature color. Melanin, the same pigment that gives your skin its tone, is present in the trapped material. When that melanin is exposed to oxygen in the air, it oxidizes and turns dark brown or black. The color isn’t dirt, and it has nothing to do with cleanliness.
Bacteria that naturally live on your skin also play a role. A species called C. acnes produces a biological adhesive that helps it form colonies inside pores. When this bacterium thrives in a clogged follicle, it contributes to the buildup of material that leads to comedones. In an open pore like a blackhead, this bacterial activity is relatively mild compared to the deeper infection you’d see in a full-blown pimple, but it’s part of the chain of events.
Why Some People Get More Blackheads
Hormones are the single biggest driver. Androgens, a group of hormones that includes testosterone, directly stimulate oil glands to grow larger and produce more sebum. This is why blackheads often first appear during puberty, when androgen levels surge. It also explains why acne can flare around menstrual cycles, during pregnancy, or during other hormonal shifts. Up to 15% of adult women deal with ongoing acne, often tied to these fluctuations.
Genetics matter more than most people realize. A large study of over 26,000 people identified 15 regions of the genome linked to developing acne. Many of those genetic variants influence hair follicle formation, not just oil production. Researchers at King’s College London found that the shape of your hair follicles may make them more prone to trapping bacteria and triggering the clogging process. One specific gene variant (WNT10A) was particularly interesting: people with one copy appeared to be protected against acne, while two copies caused a rare condition affecting hair growth. If your parents had persistent acne, your odds of dealing with blackheads go up significantly.
How Diet and Environment Play a Role
What you eat can influence how much oil your skin produces. Diets high in refined carbohydrates and sugar, measured by what researchers call glycemic load, raise blood sugar and insulin levels quickly. That insulin spike appears to stimulate sebum production. One study found that people who switched to a lower glycemic diet saw a shift in the composition of their skin oil: the ratio of certain fatty acids changed in a way that made the sebum less likely to irritate follicles. Specifically, high-carb diets increased a type of fatty acid (monounsaturated) that has been shown in lab studies to promote the kind of pore lining overgrowth seen in early blackhead formation. Diets heavy in white bread, sugary drinks, and processed snacks push this process along, while meals built around whole grains, vegetables, and protein tend to keep sebum composition more balanced.
Your environment adds another layer. Humid air traps dirt and oil against the skin, increasing the likelihood of pore blockage. Air pollution, including particulate matter and heavy metals, can penetrate the skin barrier and trigger oxidative stress and inflammation. Pollutants physically settle into pores and accelerate the oxidation that darkens comedonal plugs. If you live in a city with poor air quality or a tropical climate, your skin faces a heavier burden even before hormones and genetics enter the picture.
Blackheads vs. Sebaceous Filaments
Many people think they have blackheads on their nose when what they’re actually seeing are sebaceous filaments. These are normal structures that line your oil glands and help channel sebum to the surface. They look like tiny dark dots, but they’re typically smaller, flatter, and lighter in color than true blackheads, usually gray, light brown, or yellowish.
The key difference is structural. A blackhead contains a solid plug of oxidized sebum and dead skin that blocks the pore. If you were to extract one, a dark, waxy chunk would pop out. A sebaceous filament has no plug. Oil flows freely through it. If squeezed, it produces a thin, threadlike strand rather than a solid mass. Sebaceous filaments refill within about 30 days no matter what you do, because they’re a permanent part of your skin’s oil delivery system. Blackheads, on the other hand, are a form of acne that can be treated and prevented.
What Keeps Blackheads Coming Back
Blackheads are persistent because the factors driving them are ongoing. Your oil glands don’t stop producing sebum, your skin continuously sheds cells, and hormonal cycles repeat. Certain habits can make the cycle worse. Skincare products or cosmetics that contain heavy oils can coat the inside of pores and trap debris. Touching your face transfers additional oil and bacteria. Over-washing or scrubbing aggressively can strip the skin’s surface and trigger a rebound in oil production, making the problem worse rather than better.
Products containing salicylic acid are commonly used because they dissolve inside the pore, breaking apart the mix of oil and dead cells that forms the plug. Retinoids, which are derived from vitamin A, work differently by speeding up cell turnover so dead skin cells are less likely to accumulate in the first place. Both approaches target the root mechanics of blackhead formation rather than just removing existing plugs.
Pore strips and manual extraction can clear individual blackheads, but they don’t change the underlying conditions that created them. Without addressing excess sebum, slow cell turnover, or hormonal triggers, new blackheads will form in the same spots within weeks.