Acne almost never has just one cause. It's usually a combination of a few of these working together.
Genetics
If one or both of your parents dealt with acne, you're more likely to as well. Genetics influence how much oil your skin produces, how efficiently your pores shed dead skin cells, how easily those pores clog, and how strongly your immune system reacts to bacteria.
Some people are predisposed to acne no matter how “perfect” their routine is, and others rarely break out even with a pretty lax routine. That's genetics, not effort.
Hormones
This is one of the biggest drivers of acne at every life stage.
- Puberty
- Rising androgens stimulate the sebaceous glands to produce more oil, which sets up the perfect environment for clogged pores and bacterial overgrowth. This is why teenage acne shows up most on the forehead, nose, and chin.
- Cycle-related changes
- For anyone who menstruates, hormone levels shift throughout the month. In the days before a period, estrogen drops while progesterone and androgens take over, which increases oil production and inflammation. Androgens are really the main hormonal driver behind excess sebum.
- Adult acne
- Even when overall hormone levels look stable, the sebaceous glands can stay sensitive to androgens, so oil production and inflammation keep going. Adult hormonal acne tends to show up on the lower face, jawline, chin, and neck, and sometimes the back or chest.
- Other hormonal triggers
- Chronic stress (which raises cortisol and inflammatory signaling), PCOS, pregnancy or postpartum hormone shifts, and starting, stopping, or changing hormonal birth control.
Lifestyle
- Poor sleep raises cortisol and systemic stress, which can worsen both inflammation and oil production.
- Smoking impairs circulation and slows wound healing, which can prolong active breakouts and increase the odds of post-acne marks sticking around.
- Certain supplements, like whey protein, biotin, and B12, carry a real risk of influencing hormones or inflammation in some people.
- Sweat and friction from tight clothing, helmets, masks, straps, or sports gear can irritate the follicle and trap heat and sweat against the skin. This specific type is called acne mechanica, and it's common in athletes and anyone wearing tight or protective gear for long stretches.
Environment
Heat and humidity increase sweating and can push sebum production even higher. Air pollution and particulate matter can settle on the skin and mix with oil, which adds oxidative stress and can contribute to inflammation and clogged pores. Environment alone doesn't cause acne, but it can absolutely aggravate skin that's already prone to it.
Ingredients in products
Beyond skincare and makeup, occlusive or poorly formulated products (thick creams, certain oils, waxes, dense makeup) can physically impair how the follicle sheds, which leads to whiteheads and blackheads.
Remember, “non-comedogenic” isn't a guarantee. What matters is the actual formulation and how your skin responds over time.