Your regular family doc prescribes drugs carefully, taking care not to combine medications that would either inhibit effectiveness, or cause dangerous symptoms when used together. When it comes to skincare … same rules apply. Skincare regimens that have been formulated to work together to achieve results should be used together. Mixing and matching brands or products to create your own regimen could result in a lack of benefit as well as skin sensitivity and other undesired side effects. For best results, use as directed and remember, consistency is key.