I've been getting facials semi-regularly since I graduated college — mostly as a way to control my acne, but also to help maintain my overall skin health. Just about every pro you talk to says that facials are a cornerstone of a good skin-care regimen. Makes perfect sense.Recently I had the opportunity to get an amazing facial at L'institut Orlane in Paris. And even with all those spa days under my belt, something happened there that I'd never experienced stateside. The second the aesthetician began cleansing my face, she exclaimed, "Oh! You have sensitive skin." Never in my life had I been told this. Acne-prone? Yes. Combination? Totally. But never sensitive.The idea of sensitive skin is hotly debated in the world of skin care. In the 1980s, only 30% of people thought they had sensitive skin, says L.A.-based dermatologist Jessica Wu, MD, while today, a whopping 70% of people think they do . But most dermatologists roll their eyes at that number. Why? The keyword here is think. Only a small portion of the population actually has sensitive skin. What's more, the term "sensitive" covers a wide spectrum of issues."Sensitive skin can be caused by many different factors," says dermatologist Karyn Grossman, MD. "Sometimes, it is more of a genetic issue. People are born with genetic predispositions for rosacea, eczema, dry skin, allergies, etc." These conditions can be detected when the patient is younger, but sometimes they don't rear their heads until adulthood. Patients with eczema have what Dr. Grossman calls a "leaky" skin barrier — meaning it allows in irritants and lets out hydration. Folks with rosacea tend to have dilating blood vessels, more inflammation, and improper barrier function.All of these genetic predispositions can and should be diagnosed in the dermatologist's office — not just by looking in the mirror and guessing what you've got. (No WebMD-ing this, guys.) "Most people try to self-diagnose, but it's really something that needs to be done by a professional," says aesthetician Vanessa Hernandez. She says you can identify sensitive skin by broken capillaries — something a derm or licensed aesthetician is qualified to spot.But when you get past genetics, things get a little dicey. Dr. Grossman says certain products and treatments can cause skin to become sensitive. "Certain product ingredients can cause inflammation in the skin, causing it to be sensitive," she explains. "Other ingredients can cause dryness, triggering sensitivity. Some can do both." She adds that factors such as over-exfoliation, using water that is too hot, combining too many active ingredients, and doing too many procedures — or too many of the wrong procedures, can also cause sensitivity.Raffaella Giraudi, the world general manager of Orlane, echoes this statement. "A lot of external factors can affect skin sensitivity," she says. "Hot, cold, or wet weather, or an overreaction to stress, can cause sensitivity. Medicine and sun exposure can also cause sensitivity in the moment." Giraudi adds that travel (especially air travel) can dehydrate your skin — which explains why my aesthetician in Paris may have said my skin was sensitive.So what does this all mean? "Many people will have some sensitivity to strong ingredients," Dr. Grossman says. Which makes total sense — not everyone's skin is meant to handle every ingredient. That's why we have skin types — what works for one face won't work for another. But that doesn't mean your skin is necessarily classified as sensitive. It just means you may have a sensitivity — and that is an important distinction to make."All skin types can be sensitive," Giraudi says. It's just that each type is sensitive to different things. If you're like me and your face can handle retinol and salicylic acid — but gets a little red when you use a certain exfoliant — your skin isn't sensitive. You're just reacting to that specific exfoliant — whether it's because of an ingredient, the grade of the scrub, or something else.Dr. Grossman says that most misconceptions about sensitive skin stem from our own user errors. "A lot of this is due to over-aggressiveness by people," she says. "Many will scrub their faces twice daily, apply acids, retinoids, peels, bleaches, and just overdo it." The easiest way to see if you have a sensitivity is to patch-test on a small portion of skin. If you break out, get red, or feel itchiness or burning, set aside the product and take note of the ingredients. Over time, you may start to recognize patterns in what makes your skin freak out, which will make shopping a lot easier. And go easy on your skin, will you? No need to scrub yourself raw.The best part of this process is that once you've discerned you're not sensitive — you just have a sensitivity — you can get to work finding products that will actually benefit you. "While there won't be a huge negative impact if you're using sensitive-skin products on non-sensitive skin, it may keep you from finding ingredients that actually work for you," Hernandez says. Our two cents? You owe it to yourself to find your skin-care soul mate.