Yes, because Instant Spray-In Toners are a leave-in, protein-based conditioner formula, you can use them daily without any problems. Just be mindful, that if your hair is already cool or toned, using Colour Restore Instant Spray-In Toners will intensify those tones.
So, Ash hair will become Grey Toned, and Platinum hair will turn Metallic Silver. But remember these enhanced results only last until your next shampoo. However, they can be a great way of intensifying and perfecting an existing cool shade.