After countless trips to the dermatologist’s office, I’ve come to recognize one skin-care truth: the causes of acne aren’t always easily discernible. In a new survey released by eMediHealth—a resource for expert-reviewed health information—64 dermatologists identified the most common triggers. Some of the culprits behind painful blemishes are kind of a “no, duh” and others are—well—pretty darn surprising.

“The results of this survey are in line with what we know are truly causes of acne,” says New York City-based dermatologist Joshua Zeichner, MD. “At the most basic level, acne is caused by your hormones. We know that they stimulate activity of sebaceous glands promoting breakouts. We also know that the environment significantly impacts our skin. Psychological stress has been directly linked to acne breakouts as has dietary factors—like foods with a high glycemic index.”

The 10 most common causes of acne, according to dermatologists

1. Fluctuating hormones

Oh, hormonal acne—thou art persistent. More than 84 percent of the dermatologists survey listed hormones as a common breakout trigger.  “Hormones are the cause of almost all acne no matter what age you are,” Gary Goldfaden, MD, a Miami-based dermatologist, previously told Well+Good. “The hormones we’re talking about are primarily progesterone and estrogen, but you also have to consider cortisol, aka the stress hormone. The interaction of these three are usually the cause behind the acne.”

2. Stress

Number two is actually linked to number one—and 76 percent of dermatologists surveyed named it as a factor. The aforementioned stress hormone, cortisol, can kickstart a reaction in our bodies that ends with acne. “Stress causes a complex series of changes to our bodies.  As part of the stress response, cortisol and related hormone levels rise to prepare the body for a stressful experience,” Dr. Zeichner told Well+Good.  “As a side effect, these hormones lead to an increase in oil production in our skin promoting breakouts. They can also interfere with wound healing, prevent the skin from repairing itself, and could potentially be associated with premature aging.”

3. sugary food

Studies have linked sugar consumption to acne, and 64 percent of dermatologists in the study reported it as a top trigger for their patients.

4. dairy

Fifty-six percent of the dermatologists listed dairy as a common contributor to acne. In studies, the consumption of milk products has been associated with moderate to severe acne.

5. Cosmetic products

No surprise here! Certain cosmetics—especially of the comedogenic variety—can cause breakouts. So keep your eye out for acne-friendly foundation and other cosmetics designed for your complexion.

A derm’s take on adult acne:

6. Certain medications

Over 50 percent of the dermatologists said that certain medications, like some contraceptives, can cause acne. Talk to your doctor if you think one of your medications may be causing it.

7. menstruation

“The face is definitely singled out by the hormonal changes two weeks before a period. The hormonal surges before a period make the oil glands of the face hyperactive creating oilier skin, attracting unwanted bacteria and those dreaded monthly pimples,” Sherry A. Ross, MD, a New York City OB/GYN and author of she-ology. The Definitive Guide to Women’s Intimate Health. Period, previously told Well+Good. Forty-five percent of the dermatologists surveyed agree.

8. diet

As causes three and four illustrate, diet may play a role in acne. Some foods—like figs, olives, and plums—may actually promote skin health.

9. processed and packaged foods

The dermatologists—36 percent of those surveyed, to be precise—say that the gut-health connection is real. “When I speak to my patients about diet and its link to acne, I keep it simple,” said Miami dermatologist Roberta Del Campo, MD. “Anything that causes a spike in blood sugar can, theoretically, increase inflammation and insulin levels, therefore leading to pimples and excess oil.” Processed and packaged foods often contain high amounts of sugar, so dematologists say to do your best to eat whole foods whenever possible.

10. poor hygiene

Say you don’t shower after a particularly sweaty workout. Derms say that your skin will definitely take notice. “One of the functions of the skin is to act as a secondary channel of elimination to help rid the body of toxins,” said Milo Carter, vice president of medical at the beauty brand Lumion. “Sweat and sebum help to facilitate detoxification, which is good, but when these toxins reach the surface and aren’t cleansed away, they’ll reabsorb back into the skin.” So make sure you’re washing your skin twice day—especially after a workout.

What about acne scars?

Here’s how to create the perfect skin-care routine for acne, and the FAQ’s Dr. Pimple Popper gets all. the. time.