That's a great question. To make it short, you should use sulfates in a shampoo and use silicones in a conditioner or a serum that you will apply at the end of your washing routine. Here is the logic: Sulfates is meant to wash your hair, so this ingredient makes sense in a shampoo that has the function to clean your scalp. Then, you want to lock in the moisture and good ingredients in your hair after your wash and for that, you can use silicones by applying it with your conditioner or with a serum on damp hair after your wash (if your conditioner doesn't have silicones for example). Now, yes there are some shampoos that contain silicones but we noticed that either these silicones won't stay on your hair (directly washed by the shampoo coming with it) OR it will be super sticky no-go silicones you want to avoid anyways.