It's important to do a patch test when introducing a new product to your skin care routine. There are a number of allergens in products that can cause your skin to have an adverse reaction. You may also experience an adverse reaction to a product simply because your skin doesn’t like a specific ingredient. It can even occur from using natural products or from one that is well-formulated. Products containing synthetic dyes or fragrances, parabens, sulfates or high concentratio