What Causes Acne? Hormones, Genetics, Diet & More

If you’ve gone looking for the cause of your acne, you’ve probably been told it’s everything: your diet, your hormones, your pillowcase, your stress, your face wash. The truth is more focused — and more useful. Acne has a small set of root causes, with a longer list of factors that can influence it.

This guide separates the two.

The root cause: your pores, oil, and inflammation

At its core, acne is driven by what happens inside the pilosebaceous unit — the follicle and its oil gland. Four biological processes combine to create breakouts: excess oil production, sticky skin cells that clog the follicle, the bacterium Cutibacterium acnes, and inflammation.

Everything else — hormones, genetics, diet, stress — works by influencing one or more of these four processes. So when we ask “what causes acne,” we’re really asking: what tips these processes out of balance?

Is acne hormonal?

Yes — for most people, hormones are the single biggest driver.

A group of hormones called androgens (which everyone produces, regardless of sex) stimulate the sebaceous glands to produce more oil. This is why acne so reliably appears at puberty, when androgen levels surge, and why it flares at other hormonal moments: the menstrual cycle, pregnancy, polycystic ovary syndrome (PCOS), and starting or stopping certain medications.

You don’t need a hormonal disorder to have hormonally-influenced acne — normal hormonal fluctuations are enough to set off breakouts in acne-prone skin. That said, if acne appears alongside irregular periods, excess hair growth, or other symptoms, it’s worth discussing PCOS or other conditions with a clinician.

Is acne genetic?

Largely, yes. Genetics strongly influence whether you’ll get acne, how severe it will be, and how your skin responds. If both your parents had significant acne, you’re considerably more likely to as well.

What you inherit isn’t acne itself but a tendency — more reactive oil glands, skin cells that clog more easily, or an immune system that responds more strongly to C. acnes. This is a big part of why two people with identical diets and routines can have completely different skin. It also means acne is not something you “brought on yourself.”

Does diet cause acne?

This is where the real answer is “it’s complicated, and probably less than the internet claims.”

Diet does not cause acne the way hormones and genetics do. But a growing body of evidence suggests certain dietary patterns can influence breakouts in some people:

• High-glycemic foods (sugary drinks, white bread, refined carbs that spike blood sugar) have the most consistent evidence linking them to worse acne, likely through their effect on insulin and androgen-related hormones.
• Dairy, particularly skim milk, shows a modest association with acne in several studies, though the effect is small and not seen in everyone.

Note the word association. These links are real but modest, vary a lot between individuals, and don’t apply to everyone. Plenty of people see no change when they cut sugar or dairy.

Does sugar cause acne?

Not directly. But foods that spike blood sugar can worsen acne in susceptible people by raising insulin, which in turn can increase oil production and inflammation. A single dessert won’t break you out; a consistently high-glycemic diet might nudge things in the wrong direction. It’s a contributing factor for some, not a cause for all.

What about the other usual suspects?

A few factors can genuinely aggravate acne — though they rarely start it:

• Stress doesn’t cause acne, but it can worsen existing breakouts through cortisol and inflammation.
• Friction and pressure (masks, helmets, phones, picking) can trigger or worsen lesions.
• Comedogenic skincare and makeup — pore-clogging ingredients — can contribute to breakouts.
• Certain medications, including some steroids and hormonal treatments, can cause acne as a side effect.
• Sweat left on the skin can contribute, though sweat itself isn’t the villain it’s made out to be.

What does NOT cause acne

Just as important: some widely-blamed culprits aren’t real causes.

• Poor hygiene. Acne is not caused by dirty skin, and over-washing actually irritates skin and can make acne worse.
• Chocolate, specifically, as a unique villain (it’s the overall glycemic load that may matter, not chocolate itself).
• Greasy foods giving you greasy skin — eating oil doesn’t directly translate to facial oil.

The bottom line

Acne is primarily caused by hormones and genetics acting on the biology of your pores. Diet, stress, friction, and skincare can influence it, but they’re contributing factors rather than root causes — and their impact varies enormously from person to person. Hygiene isn’t the issue, and neither is anything you did wrong.

The practical takeaway: address the biology (with appropriate treatment) first, and tune the lifestyle factors that seem to affect your skin specifically.