As going " gluten-free " becomes ever more popular, we're learning a lot about what it means to have celiac disease. But, as Jennifer Esposito learned the hard way, diagnosing celiac can be a long, devastating process.As the actress explains in an upcoming episode of Oprah: Where Are They Now?, she had been experiencing a long list of bizarre symptoms. And when a tooth randomly fell out of her mouth while filming Samantha Who?, she knew it was time to get medical help."My hair was falling out, my eyelashes fell off, my fingernails were falling off," Esposito explains . "I was bad.”Celiac disease is a condition in which your body's immune system reacts when you eat gluten. Over time, those reactions can cause a lot of damage. Often, that includes gastrointestinal symptoms, such as severe bloating and diarrhea.But that's not always the case. Sometimes, people with celiac have broader symptoms , such as fatigue, itchy skin, joint pain, and even anemia. So it's not always obvious that they even have a GI issue at all. Celiac is truly a serious condition, and treating it requires strictly adhering to a gluten-free diet for the rest of your life.That's why it's a little disconcerting that gluten-free has become such a trend. A study published just this week in JAMA Internal Medicine found that the number of Americans ditching gluten rose from .52% to 1.69% between 2009 and 2014. But the amount of people with celiac held steady, which suggests more and more people (mostly young, white women ) are taking on this diet unnecessarily.Of course, if you think gluten might be the root cause of any unpleasant symptoms in your life, definitely check in with your doctor. And please don't go off gluten without his or her input.