It’s basic chemistry: oil and water don’t mix. If you use a water-based moisturizer and a silicone-based foundation, the silicone will eventually "slip" off the water layer, causing separation on the nose and chin. Check your ingredients: Dimethicone = Silicone. Aqua = Water. Go check your makeup bag right now. Drop a comment below with your favorite primer and foundation combo—let’s audit them to see if they are chemically compatible!