Products may claim to repair damage, but they generally cannot. Protein-treatments(and those with silicones) fill in weakened areas of damaged strands, making them appear thicker and fuller, but they don't permanently BIND to the hair. It's a very temporary fix that once rinsed (shampooed) out, leaves you back to square one and sometimes dependent on that product to give you consistent (although short-lived) results. Damage hair can't be repaired. The best way to treat damage is to remove it and utilize a routine(which includes products) that minimizes over-manipulation which minimizes potential damage sustained.