Blackheads form when a pore gets clogged with a mix of oil and dead skin cells, and the surface of that plug darkens after exposure to air. They’re not caused by dirt, and washing your face more won’t prevent them. Around 85% of people between ages 12 and 24 deal with some form of acne, and blackheads are one of the most common types.
How a Blackhead Forms Inside a Pore
Every pore on your skin contains a tiny oil gland that produces sebum, a waxy substance designed to keep your skin moisturized. Under normal conditions, sebum travels up through the pore and spreads across the surface of your skin without issue. Problems start when your body produces too much sebum or when dead skin cells don’t shed properly and accumulate inside the pore instead of sloughing off.
When excess oil and dead skin cells build up together, they form a plug that partially blocks the pore opening. Unlike whiteheads, where the pore is sealed shut, blackheads remain open at the surface. That open top is what gives them their defining characteristic: the dark color that makes them look like specks of dirt embedded in your skin.
Why Blackheads Look Dark
The dark color has nothing to do with dirt. It comes from a chemical reaction between the contents of the plug and the air. Sebum contains a fat called squalene, which is the most easily oxidized of all the lipids on your skin’s surface. When squalene sits at the top of an open pore and meets oxygen (and especially UV light), it converts into squalene peroxide, a compound that darkens in color. The melanin already present in the dead skin cells within the plug adds to the effect. The deeper in the pore the material sits, the lighter it stays, which is why only the visible surface turns black or dark brown.
Hormones Are the Biggest Driver
Your oil glands have receptors for androgens, a group of hormones that includes testosterone and its more potent form, dihydrotestosterone (DHT). When androgen levels rise, these hormones bind to receptors on immature oil gland cells and trigger them to produce more lipids, including the triglycerides and squalene that make up sebum. This is why blackheads tend to show up during specific life stages and hormonal shifts.
Puberty is the most obvious example. The surge in androgens between ages 12 and 24 drives oil production up dramatically, which is why acne peaks during those years. But hormonal fluctuations don’t stop there. Around 50% of women in their 20s, 33% in their 30s, and 25% in their 40s still deal with acne. Menstrual cycles, pregnancy, polycystic ovary syndrome, and even stress (which raises cortisol and can indirectly boost androgen activity) all influence how much oil your glands pump out.
Diet Plays a Supporting Role
What you eat can change both how much sebum you produce and what that sebum is made of. Diets high in refined carbohydrates and sugar (think white bread, sugary drinks, pastries) have a high glycemic load, meaning they cause rapid spikes in blood sugar and insulin. Those insulin spikes trigger a hormonal cascade that can stimulate oil glands in much the same way androgens do.
Research on low glycemic load diets found that changing the type and amount of carbohydrates people ate altered the fatty acid composition of their sebum within 12 weeks. Specifically, people eating fewer refined carbs had a higher ratio of saturated to monounsaturated fats in their sebum, and that shift correlated with fewer acne lesions. Higher sebum flow was also associated with more monounsaturated fatty acids in the oil. In practical terms, diets heavy in processed carbs may make your sebum more prone to clogging pores and oxidizing.
Products That Clog Pores
Some skincare and hair products contain ingredients that are comedogenic, meaning they physically block pores regardless of how they’re formulated. Common culprits include certain forms of lanolin (often found in heavy moisturizers), coconut oil, and some thickening agents like agar. The comedogenic nature of an ingredient doesn’t change based on the overall product formula. If the ingredient clogs pores on its own, it will do so in a serum, a cream, or a shampoo that drips onto your forehead. If you’re prone to blackheads along your hairline, forehead, or jawline, the products you use on your hair and skin in those areas are worth examining.
Sebaceous Filaments Are Not Blackheads
Many people mistake sebaceous filaments for blackheads, especially on the nose. Sebaceous filaments are thin, threadlike structures that line your oil glands and help channel sebum to the skin’s surface. They’re a normal part of your skin’s anatomy, not a type of acne. They can look like tiny dark spots, but they’re typically smaller, flatter, and lighter in color than blackheads, usually gray, light brown, or yellowish rather than dark black.
The key difference is structural. Blackheads contain a solid, waxy plug that blocks the pore. Sebaceous filaments have no plug, so oil flows through them freely. If you squeeze a sebaceous filament, a thin, threadlike strand of wax comes out, but it refills within about 30 days because the structure is supposed to be there. Squeezing a blackhead produces a darker, firmer plug. Trying to extract sebaceous filaments is pointless and can irritate or enlarge pores over time.
What Actually Clears Them
Because the plug inside a blackhead is made of oil and dead skin, the most effective treatments work by dissolving that plug from within or preventing it from forming in the first place. Salicylic acid is the go-to ingredient because it’s oil-soluble, meaning it can penetrate into the pore lining rather than just sitting on the skin’s surface. Over-the-counter products typically contain 0.5% to 2% salicylic acid in lotions and solutions, applied one to three times daily.
Retinoids (vitamin A derivatives available in both prescription and over-the-counter strengths) work differently. They speed up the turnover of skin cells so dead cells are less likely to accumulate inside pores. This addresses one half of the clogging equation. The tradeoff is an adjustment period of several weeks where skin may feel dry or irritated before it adapts.
What doesn’t work well: scrubbing, pore strips, and aggressive squeezing. Physical scrubbing can irritate skin and trigger more oil production. Pore strips pull out the surface of the plug but leave the deeper portion intact, so the blackhead returns quickly. And squeezing risks pushing material deeper into the pore, causing inflammation or scarring. The most effective long-term approach combines a chemical exfoliant like salicylic acid with a non-comedogenic moisturizer and, if hormonal factors are significant, addressing those underlying triggers.