Pimples form when oil, dead skin cells, and bacteria build up inside a hair follicle and trigger inflammation. That’s the short answer, but the reason you’re breaking out right now likely involves a specific combination of hormones, genetics, diet, stress, or products you’re putting on your skin. Understanding which factors are driving your acne makes it much easier to address.
What Actually Happens Inside a Pore
Every pimple starts the same way. Your skin’s oil glands produce a substance called sebum, which normally travels up through your pores to moisturize the surface of your skin. Problems begin when one of three things goes wrong: your glands produce too much oil, dead skin cells accumulate and plug the pore’s opening, or bacteria multiply inside the clogged pore. In most cases, all three happen together.
Once a pore is blocked, the trapped oil and dead cells create a perfect environment for bacteria that naturally live on your skin. As those bacteria feed and multiply, your immune system responds with inflammation. That’s what produces the redness, swelling, and tenderness you see and feel. A shallow blockage near the surface becomes a whitehead or blackhead. When inflammation goes deeper, you get the more painful, raised bumps.
Hormones Are the Most Common Driver
Androgens, a group of hormones present in both men and women, are the primary trigger for excess oil production. Your oil glands contain enzymes that convert weaker hormones into a potent form called dihydrotestosterone (DHT), and skin that’s prone to acne has higher levels of these converting enzymes than clear skin does. When DHT binds to receptors in the oil gland, it ramps up sebum output.
This is why acne peaks during puberty, when androgen levels surge. But hormonal acne doesn’t end with your teenage years. Up to 20% of women and 8% of men over age 25 deal with clinical acne. For women, breakouts often flare in patterns tied to the menstrual cycle, pregnancy, or polycystic ovary syndrome, all of which shift androgen levels. If your pimples cluster along the jawline and chin and worsen around your period, hormones are a likely culprit.
Your Genetics Set the Stage
A large twin study found that roughly 85% of the variation in acne severity is explained by genetics. That means if your parents had significant acne, your odds of dealing with it are high regardless of how well you take care of your skin. What you inherit isn’t just a tendency toward oily skin. It includes the size and activity of your oil glands, how quickly your skin cells turn over, and how aggressively your immune system responds to clogged pores.
This doesn’t mean your breakouts are entirely out of your control. It means that some people can eat pizza and skip their face wash with no consequences, while others do everything right and still break out. If that sounds like you, it’s not a failure of hygiene. It’s biology.
How Diet Can Make Breakouts Worse
Two dietary patterns have the strongest links to acne: high-sugar foods and dairy.
Foods that spike your blood sugar quickly (white bread, sugary drinks, candy, white rice) cause your body to release a burst of insulin. That insulin triggers a cascade that increases a growth hormone called IGF-1, which in turn stimulates your oil glands to produce more sebum. In a controlled trial, participants who switched to a low-glycemic diet for just two weeks saw a measurable drop in IGF-1 levels compared to where they started.
Dairy works through a similar pathway. Milk and dairy products contain proteins that raise both insulin and IGF-1 levels. They also contain naturally occurring hormones, including androgens, that can further stimulate oil production. A meta-analysis of observational studies confirmed the association between dairy intake and acne development. Skim milk appears to be more strongly linked than full-fat milk, possibly because of the whey protein concentration.
None of this means you need to overhaul your entire diet overnight. But if you’re breaking out persistently and can’t figure out why, paying attention to how much sugar and dairy you consume for a few weeks can be revealing.
Stress Breakouts Are Real
When you’re under stress, your body releases cortisol and a related hormone called corticotropin-releasing hormone (CRH). CRH doesn’t just circulate in your bloodstream. It’s produced directly in the oil glands of acne-prone skin at much higher levels than in unaffected skin. CRH stimulates sebum production and activates enzymes that convert other hormones into androgens right there in the gland.
This explains why breakouts often follow stressful periods with a short delay. The stress hormone surge increases oil output, which takes a few days to clog pores and develop into visible pimples. If you notice breakouts appearing a week or so after a rough stretch at work, an exam period, or a major life event, the timing isn’t coincidental.
Products That Clog Your Pores
Some skincare and hair products contain ingredients that physically block pores, a property called comedogenicity. Heavy moisturizers, certain sunscreens, pomades, and even some foundations contain oils and waxes that sit in the follicle opening and trap sebum underneath. Common offenders include acetylated lanolin, coconut oil, and cocoa butter.
If your breakouts concentrate in areas where you apply products heavily, like your forehead near the hairline (from hair products), your cheeks (from foundation), or your chin (from heavy moisturizer), your routine might be part of the problem. Look for products labeled “non-comedogenic,” and consider simplifying your regimen temporarily to see if your skin improves.
Friction matters too. Regularly pressing your phone against your cheek, wearing tight hats or headbands, or resting your chin in your hands can push bacteria and oil deeper into pores. This type of acne, sometimes called acne mechanica, shows up exactly where the pressure occurs.
Different Types of Pimples Mean Different Things
Not all breakouts are the same, and knowing what type you’re dealing with helps you understand how serious it is.
- Blackheads and whiteheads: These are clogged pores without much inflammation. Blackheads are open at the surface (the dark color is oxidized oil, not dirt). Whiteheads are closed. Both are mild and usually respond to over-the-counter treatments.
- Papules: Small, raised, discolored bumps that feel tender. They’re inflamed but don’t contain visible pus.
- Pustules: Similar to papules but with a white or yellow pus-filled center. These are what most people picture when they think of a pimple.
- Nodules: Large, painful lumps that form deep under the skin. You can feel them before you see them, and they don’t come to a head.
- Cysts: Deep, pus-filled lumps beneath the skin’s surface. Cystic acne is the most severe form and is the most likely to leave permanent scars.
Blackheads, whiteheads, and occasional pustules are normal and manageable with consistent skincare. Nodules and cysts that recur, especially if they leave dark marks or scarring, typically need professional treatment because the inflammation occurs too deep for topical products to reach effectively.
Why You Might Be Breaking Out Right Now
If your pimples are new or have suddenly gotten worse, think about what’s changed recently. A new skincare product, a shift in diet, increased stress, a medication change (especially starting or stopping hormonal birth control), or even moving to a more humid climate can all trigger breakouts. Hormonal shifts are particularly common triggers for adult women who never had acne as teenagers.
If your acne has been persistent for months or years and isn’t responding to over-the-counter products containing benzoyl peroxide or salicylic acid, the cause is likely hormonal, genetic, or both. These deeper drivers don’t respond well to surface-level treatments alone and benefit from a dermatologist’s evaluation, where options exist to address the hormonal and inflammatory processes fueling the breakouts from the inside.