Have you ever caught sight of yourself after a long day and noticed patches of your foundation caking into your creases or that there are unsightly streaks on your nose where your makeup has separated? Welp. One culprit behind why your glam could be clumping up is because the ingredients in your primer and your foundation might be incompatible with each other.

Most primers are formulated with either oil, silicone, or water. Oil-based ones are usually marketed as “moisturizing” or “hydrating,” and if you look on the ingredients list, you tend to find the word “oil” or “-oleate” amongst the top components. Meanwhile, if you’ve got a silicone product, they tend to be marked as “HD,” “smoothing,” or “long-lasting.” The list will start with a lot of words with “-silicate,” “-cone,” or “-siloxane.” Lastly, water-based formulas typically have “oil-free” and “silicone-free” on the packaging, and aqua is usually at the top of its ingredients. If a product has all three ingredients, the one that’s listed higher up means it is more prevalent.

So, how do you know which primer to choose? Oilier, acne-prone skin types might want to try sticking to water-based products, while drier skin can opt for oil-based. Silicone can sometimes cause congestion, but it’s a dream at creating a smooth canvas for special events. Regardless of the primer you choose, it’s important to always, always be on the lookout for a non-comedogenic label. This means the product won’t clog your pores, nor will it be as likely to clump in general.

Word to the wise: Never mix water-based primers with oil or silicone makeup and vice versa. That, therein, is your cause for separation. Just like in your childhood science experiments, water and oil (and silicone) repel each other, hinting at why your face makeup may look less than flawless by the end of the day.

Now that you better understand why your makeup is functioning (or, rather, malfunctioning) as it is, let’s chat combos. Below are some of our suggestions for primers and foundations that go hand-in-hand and won’t separate throughout the day.

1. Silicone-Based Primer + Foundation: While there are plenty of awesome options on the market for silicone primers, one that really zaps the appearance of your pores and makes your makeup go on smooth as butter is Benefit’s The Porefessional ($31). (Hourglass Mineral Veil ($54) and Maybelline New York Baby Skin Instant Pore Eraser Primer ($7) are great options too.) Then for foundation, try Fenty Beauty Pro Filt’r Soft Matte Longwear Foundation ($34), Rihanna’s beauty collection’s hero product. It provides medium to heavy coverage and is buildable. Most importantly, it won’t crease or crack (with the right primer of course) after a long day. Other much-loved options are the Giorgio Armani Luminous Silk Foundation ($64) and Revlon ColorStay Makeup ($7).

2. Oil-Based Primer + Foundation: For those looking for a more moisturizing formula, Smashbox Primer Oil ($42) is a fan favorite (it has over 10K loves on Sephora). You can also try MAC Cosmetics Prep + Prime Essential Oils Grapefruit & Chamomile ($27) or radiance-boosting Tarte Radiance Drops ($32). Pair any of these primers with Lilah B. Marvelous Matte Foundation ($54), the clean beauty brand’s new, heavier coverage cream foundation, made with brightening rosehip seed oil and protective avocado oil. While the foundation is formulated with oils, it dries with a natural, powdery finish. We’re also partial to Burt’s Bees Goodness Glows Full Coverage Liquid Makeup ($17), which contains moisturizing meadowfoam seed oil.

3. Water-Based Primer + Foundation: For sensitive, oilier complexions, water-based is your best bet. TooFaced Hangover 3-in-1 Setting Spray ($32) is made with coconut water and works as a prep and setting spritz. You can also try Clarins Beauty Flash Balm ($48) or NYX HD Studio Photogenic Primer Base ($17). In terms of foundation, Makeup For Ever’s Water Blend Face & Body Foundation ($43) is a beloved water-based formula that comes in 20 shades. Or try BECCA Cosmetics Aqua Luminous Perfecting Foundation($44), which is made with water and hyaluronic acid.

Have you tried any combinations that really work? Tweet us @BritandCo!

Brit + Co may at times use affiliate links to promote products sold by others, but always offers genuine editorial recommendations.

(Photos via Getty)