The most promising correlation is, perhaps surprisingly, sugar. “Multiple studies have now found that diets with a high glycemic load can trigger acne in certain persons,” says Rajani Katta, a clinical professor of dermatology at the University of Texas at Houston. Anne Chapas, the founder of Union Square Laser Dermatology, agrees. “The spikes in blood sugar which arise from eating high-glycemic foods causes oil production, which in turn causes acne,” she says. “We know that those cause a harmful hormonal environment.”

High-glycemic foods are foods such as white bread, potatoes, and white rice, which all cause a quick rise of glucose in the blood, or what is more colloquially known as a blood-sugar spike. This blood-sugar spike also causes an increase of insulin, and that insulin spike, in turn, stimulates the activity of the hormone androgen and a protein known as insulin-like growth factor 1. These act together to encourage the growth of skin cells and the production of an oily glandular secretion called sebum. And that combination of skin growth and oil production—you guessed it—can lead to acne.

The multitude of SkincareAddiction Redditors ditching milk to cure their pimple problems might have the right idea. “Limited evidence suggests that some dairy, particularly skim milk, may influence acne,” the AAD advises. Only a few studies have been conducted looking at the connection between dairy and acne prevalence, and none of them was both randomized and controlled. But they all discovered, more or less, that the regular consumption of milk, particularly skim milk, appears to worsen acne. Cheese and yogurt don’t seem to have an effect one way or another.

I asked Abigail Rapaport, a senior dietician at Mount Sinai Hospital, why there have been so few studies connecting acne and dairy. “Nutrition studies are hard to research in general,” she said. “Most of the research is on teens, and acne can be multifactorial, so you can’t say it’s only from dairy.”

So while the connection between milk and acne isn’t a myth, a lot more research is needed to confidently tell acne sufferers to give up lattes. Still, myths abound: that eating gluten or greasy foods can cause acne, for example, or that chocolate will worsen your breakouts.

Katta recently surveyed her patients, and found that “90 percent think there’s a link between diet and acne, and most of them think there’s a link between chocolate and greasy foods and breakouts.” But unless you’re rubbing the hamburger all over your face, greasy food on its own likely isn’t the problem. “Eating greasy food has little to no effect on acne,” the Mayo Clinic advises. “Though working in a greasy area, such as a kitchen with fry vats, does because the oil can stick to the skin and block the hair follicles. This further irritates the skin or promotes acne.”