Silk Keratin Smooth Protection Shampoo It is generally recommended to use sulfate-free shampoos after getting a keratin treatment, as sulfates can strip the keratin from the hair. Inova Professional Sulfate-Free Shampoo Silk Keratin Smooth Protection Shampoo with coconut oil and vitamin C may be a good choice for maintaining the results of a keratin treatment. Coconut oil and vitamin C can help to nourish and protect the hair, while the sulfate-free formula will help to preserve the keratin in the hair. It is important to follow the instructions provided by your stylist for the best results and to maintain the longevity of your keratin treatment.