5 Skin-Care Ingredients You Should Never Mix - and 4 You Should

Jenn Sinrich

As a beauty writer, my vanity, medicine cabinet, bedside table, and nearly every other drawer or empty box in my apartment is filled to the brim with makeup and skin-care products. What can I say? I'm a little obsessed. Plus, it's kind of my job to try different products, right? At least that's how I justify it.

Still, one thing I've learned over the years of trying and testing just about every single product line I can get my hands on is that there's no one-size-fits-all: what works for your skin might not work for someone else's, especially when mixing and matching is involved.

I had to learn the hard way: after breaking out and getting greasier than an empty pizza box after using a cleanser, toner, serum, moisturizer, eye cream, and face mask from a myriad of different companies as part of my daily and weekly regimen. I realized I was doing something (or many things) wrong.

I went to see my derm, whose first question was: which skin-care products are you using? I gave her the full list. That's when she explained to me that this hybrid of formulas was most likely the culprit. "Some active ingredients used in skin-care products can act as irritants when mixed with others, particularly in individuals with sensitive skin," explained Joyce Imahiyerobo-Ip, M.D., Director of Cosmetic Dermatology at South Shore Medical Center.

That's not to say you can't use more than one line of product - it's just that you have to consider which ingredients each product and brand contains and whether or not that combination could wreak havoc on your skin. Combining skin-care ingredients that don't go together can lead to more than just breakouts and greasiness, but also redness, flakiness, burning, or, at the very least, will cause the ingredients to cancel each other out, leaving you without so much as a little added moisture at most. To help you achieve a healthy, clear glow, we asked skin-care insiders to reveal the ingredient combinations that are more powerful when used together and the ones that lead to adverse effects when slathered together.