What Causes Acne? 7 Trigger Areas Ranked by Evidence

You've tried the cleanser. You've cut the sugar. Maybe you've seen a dermatologist for years. And still, the breakouts come back.

Finding what causes acne works a lot like a detective case. There are several suspects, and each one left behind a different amount of evidence. Some left fingerprints. Some left a vague rumor. So let's line up all seven suspects and sort them by how strong the evidence against them really is.

First, how we grade the evidence

1. Strong: named in clinical guidelines, or backed by twin studies and large genetic analyses
2. Moderate: consistent links in randomized trials or meta-analyses, but mostly observational data
3. Weak: small observational studies, mixed results, or trials that found no link

Here's the surprise once you line them up. Only three suspects reach the strong level: genetics, excess androgens, and certain medications. Most of the habits you can change at home sit at moderate or weak.

1. Genetics

This suspect left the clearest evidence. In a study of 1,557 female twin pairs, genes explained 81% of acne risk (Bataille 2002). If a parent or sibling had bad acne, this suspect is probably already at the scene. You can't change it, but it tells you how much room your habits might have to work with.

2. Hormones and body

Excess androgens are a strong-level suspect. Period timing also lives here: in one study, 44% of 400 women said their acne got worse before their period (Stoll 2001). If your cycle is irregular or your acne suddenly got much worse, it's worth talking to a dermatologist.

3. Medications

Some medications have a well-established link to acne, so this one is strong too. If breakouts showed up soon after you started something new, it's worth a closer look. Don't stop any medication on your own, though. Bring it up with the doctor who prescribed it.

4. Diet

Moderate. A meta-analysis of observational studies found an odds ratio of 1.28 for milk and acne (Juhl 2018). That's a link, not a conviction. The 2024 AAD acne guidelines didn't make any recommendations on diet or lifestyle at all.

5. Cleansing and products

Weak. A trial compared washing once, twice, and four times a day and found no meaningful difference between them (Choi 2006). Washing more didn't mean fewer breakouts.

6. Sleep and daily rhythm

Also weak. An 18-study review found that sleep and acne are linked in both directions (Samaniego 2025). Poor sleep might feed breakouts, or breakouts might ruin your sleep. No effect size was reported, so the jury's still out.

7. Contact and environment

Friction is a moderate-level suspect. A meta-analysis of 37 studies and 29,557 people found that 31% had mask-related acne (Justin 2022). If your breakouts cluster where something keeps touching your face, like your cheeks or chin, start here.

So where should you look first?

The seven suspects split into two groups.

1. Hard to change with habits: genetics, hormones, medications
2. Worth testing with habits: diet, cleansing and products, sleep, contact and environment

If your strongest suspects are in the first group, a dermatologist will likely get you further than trial and error at home. If they're in the second group, you can run your own experiment. The rule is simple: change one thing at a time. Drop milk, change how often you wash, and fix your sleep all in the same month, and you'll never know which one mattered.

We'll take a closer look at each suspect in its own post.

Find your lead suspect

The top suspect is different for everyone. Two people with the same breakouts can have completely different triggers. If you want to know which of the seven areas scores highest for you, the Acne Cause Report walks you through 40 questions in about 10 minutes and shows where to start looking.

References

1. Bataille 2002, The influence of genetics and environmental factors in the pathogenesis of acne: a twin study of acne in women, The Journal of Investigative Dermatology
2. Stoll 2001, The effect of the menstrual cycle on acne, Journal of the American Academy of Dermatology
3. Juhl 2018, Dairy Intake and Acne Vulgaris: A Systematic Review and Meta-Analysis of 78,529 Children, Adolescents, and Young Adults, Nutrients
4. Choi 2006, A single-blinded, randomized, controlled clinical trial evaluating the effect of face washing on acne vulgaris, Pediatric Dermatology
5. Samaniego 2025, Sleep Disturbances and Acne: A Comprehensive Review, Dermatology Practical & Conceptual
6. Justin 2022, Facial dermatoses induced by face masks: A systematic review and meta-analysis of observational studies, Contact Dermatitis
7. AAD 2024 acne guidelines