A new study has linked rosacea, a chronic skin condition characterized by redness of the face, to Parkinson’s disease.

The study found that those with rosacea were twice as likely to get Parkinson’s as those who did not have the condition, based on a survey of 5 million Danes, according to a JAMA Network Journals statement.

Rosacea affects up to 10 percent of people with light skin, making it one of the most common skin conditions out there.

Scientists are fairly certain that it is rosacea itself rather than medications used to treat it that likely results in more Parkinson’s diagnoses.

But they aren’t sure what the connection is for one simple reason: scientists don’t know the underlying cause behind either condition. The good is, the fact that they have been linked together perhaps gives scientists a better shot of figuring out what those underlying causes are.

One possibility is that rosacea increases the levels of a certain type of enzyme that breaks down proteins and also has a role in Parkinson’s.

There’s no proof that rosacea actually causes Parkinson’s, just that the two seem to go hand in hand surprisingly often.