Red wine headaches have been a mystery to scientists for centuries, but researchers at the University of California believe they may have finally solved the riddle. According to a study published in the journal Nature Communications, a naturally occurring compound called quercetin found in red wine may be responsible for inducing headaches.

Quercetin is an antioxidant and type of flavanol that gives fruit and vegetables their color. When combined with red wine, it can disrupt a person’s ability to break down alcohol, leading to migraines, flushes, nausea, and headaches.

Dr. Apramita Devi and Professor Andrew Waterhouse from the university’s viticulture and enology department conducted the study and discovered that when quercetin gets into your bloodstream, it is converted into quercetin glucuronide which blocks the metabolism of alcohol. This conversion can also cause acetaldehyde, a toxic byproduct of alcohol metabolism, to accumulate in the body. High levels of acetaldehyde can lead to facial flushing, headache, and nausea.

However, not all red wines are created equal when it comes to triggering headaches. The study found that wines from sunnier regions tend to have higher concentrations of quercetin which makes them more likely to cause near-immediate headaches. Additionally, age and the winemaking process can also influence whether a glass will trigger a headache or not.

Professor Morris Levin from the study’s co-author stated that people with pre-existing migraines or other headache conditions are more likely to suffer from red wine headaches as well. He said “We think we are finally on the right track toward explaining this millennia-old mystery.” The next step is now to test this scientifically on people who develop these headaches.

Overall this discovery could help individuals avoid certain types of red wine or take steps to mitigate their risk of experiencing red wine headaches in the future.