I don't know if it's a protein conditioner, but it is a good leave-in. Just don't use it too much or your hair will break from too much protein, like mine. Hope this helps.
I think the infusium does contain protein, and that's why it makes your hair hard if you use too much..I use it after every wash (condition only or shampoo) and I haven't seen any adverse effects as long as I don't use too much!