Prioritize products containing hydrolyzed keratin, which has a smaller molecular weight for better penetration into the hair shaft. Ensure the formula is sulfate-free and paraben-free to prevent stripping the hair of its natural oils and the keratin treatment itself. Look for supplementary nourishing agents like Argan oil, Collagen, or Amino Acids to enhance shine and elasticity. For professional B2B sourcing, request a full Ingredient List (INCI) to verify the concentration of active ingredients.