Blackheads form when a pore fills with a mix of dead skin cells and oil, and the surface stays open to the air. That exposure to oxygen is what turns the plug dark, not dirt. The process involves several biological steps, and multiple factors from hormones to genetics to environment can make it worse.
How a Blackhead Forms Inside the Pore
Every hair follicle on your face contains a tiny oil gland that produces sebum, a waxy substance that keeps skin moisturized. Normally, sebum travels up through the pore and spreads across the skin’s surface. A blackhead starts when that flow gets disrupted.
The first stage is invisible. Skin cells lining the inside of the pore begin to multiply and shed faster than usual, a process called follicular hyperkeratinization. Instead of shedding and washing away, these cells stick together and form a tiny plug deep in the pore. This microscopic blockage, called a microcomedo, is the precursor to every type of acne lesion.
As more dead cells and sebum accumulate behind the plug, the pore stretches. If the opening stays sealed over, you get a whitehead (closed comedone). But if the pore widens enough that the plug is exposed to air, it becomes a blackhead (open comedone). The material at the surface oxidizes, and because it contains melanin pigment and certain fatty molecules like squalene, the reaction with oxygen turns it yellow, brown, or black. The darker the color, the longer the buildup has been sitting and oxidizing.
Why Hormones Play a Central Role
Sebum production is driven largely by androgens, a group of hormones that includes testosterone. Androgen receptors sit on the oil glands themselves, and when androgens bind to those receptors, the glands ramp up oil output. This is why blackheads tend to appear during puberty, when androgen levels surge, and during other hormonal shifts like menstrual cycles or polycystic ovary syndrome.
Not all areas of the face respond to androgens equally. Research on human facial skin found significantly higher androgen receptor expression in the T-zone (forehead, nose, chin) compared to the outer cheeks and jawline. That’s a direct explanation for why blackheads cluster on the nose and forehead: the oil glands in those areas are more sensitive to hormonal signals and produce more sebum in response.
Genetics Set the Baseline
A large twin study involving over 1,500 pairs of female twins found that 81% of the variability in acne could be attributed to genetic factors, with the remaining portion driven by environment. What’s inherited isn’t blackheads themselves but the underlying tendencies that cause them: how much sebum your glands produce, how quickly your skin cells turn over inside the pore, and how your immune system responds to bacteria living on the skin.
Specific gene variants linked to acne affect the inflammatory signals that kick off the whole process. Certain polymorphisms in the genes for interleukin-1 alpha and interleukin-8, two immune signaling molecules, are associated with increased keratinocyte activation and the hyperkeratinization that starts comedone formation. If your parents had persistent blackheads or acne, you’re more likely to as well.
Diet and Insulin
High-glycemic foods like white bread, sugary drinks, and processed snacks cause rapid spikes in blood sugar and insulin. Elevated insulin does two things relevant to blackheads: it stimulates androgen production (which increases sebum), and it promotes the overgrowth of skin cells lining the pore. Early research showed that switching to a low-glycemic diet improved hormonal and skin markers of acne in young men.
That said, the effect may be modest. A controlled trial comparing low-glycemic and high-glycemic diets found that both groups saw improvement in acne (26% and 16% reduction respectively), but the difference between the two diets wasn’t statistically significant. Diet likely plays a supporting role rather than being a primary cause for most people.
Air Pollution and Environmental Triggers
Living in a polluted city can measurably affect your pores. Studies have linked higher concentrations of fine particulate matter (PM2.5 and PM10) and nitrogen dioxide to increased sebum secretion and a higher number of acne lesions. These pollutants generate oxidative stress in the skin, triggering inflammation and accelerating the breakdown of protective lipids.
One fatty molecule in sebum, squalene, is particularly vulnerable. Making up 10 to 15% of sebum, squalene is readily oxidized by ozone, UV radiation, and tobacco smoke. The byproducts of squalene oxidation are comedogenic, meaning they directly promote pore clogging, and also trigger further inflammation. Research in Shanghai and Mexico City found that chronic pollution exposure reduced protective squalene and vitamin E levels in the skin while raising overall sebum output.
Skincare Products That Clog Pores
Some ingredients commonly found in everyday products are known to promote comedone formation. In facial cleansers, anionic surfactants, lauric acid, and stearic acid are among the most frequently identified comedogenic ingredients. In moisturizers, glyceryl stearate is the most common pore-clogging culprit. These ingredients can disrupt the skin barrier and contribute to the same kind of buildup that leads to blackheads.
If you’re prone to blackheads, look for products labeled “non-comedogenic.” While that term isn’t regulated with perfect consistency, it generally means the formulation has been designed to avoid ingredients most likely to block pores.
Blackheads vs. Sebaceous Filaments
Many people mistake sebaceous filaments for blackheads, especially on the nose. Sebaceous filaments are a normal structural part of every pore. They’re tiny channels that move sebum from the oil gland to the skin’s surface, and everyone has them. Blackheads are a form of acne caused by an actual blockage.
The differences are visible once you know what to look for. Blackheads are slightly raised, feel hard on top, and have distinctly dark coloring at the surface. Sebaceous filaments are flat, smooth, and much lighter in color, typically a uniform grayish or yellowish tone without a darker cap. Blackheads can be extracted and won’t necessarily return in the same spot. Sebaceous filaments refill within about 30 days because they’re part of your skin’s normal oil-transport system, not a malfunction.
How Blackheads Are Treated
The most widely used over-the-counter treatment is salicylic acid, a beta-hydroxy acid that’s oil-soluble, meaning it can penetrate into sebum-filled pores in a way that water-soluble acids cannot. Once inside the pore, it dissolves the clumped dead skin cells that form the plug. Products containing 2% salicylic acid, applied twice daily, are the standard concentration used in clinical settings and have demonstrated measurable reductions in comedones over three weeks of consistent use.
Retinoids, available both over the counter (adapalene) and by prescription, work differently. They speed up skin cell turnover and prevent the cells lining the pore from sticking together in the first place, addressing the hyperkeratinization stage before a plug can form. Because they target the root mechanism, retinoids are often the most effective long-term option for people who get blackheads repeatedly.
Physical extraction by a dermatologist or trained esthetician can clear existing blackheads quickly, but without addressing the underlying causes, new ones tend to form. The most effective approach combines regular use of a pore-clearing product with attention to the contributing factors you can control: choosing non-comedogenic skincare, managing oil production, and minimizing environmental oxidative stress through antioxidant products or basic protective measures like sunscreen.