Kerastase Resistance Bain Extentioniste Shampoo Strengthen hair from the inside out with Kérastase Resistance Bain Extentioniste, a fortifying shampoo that uses powerful amino acids and ceramides to improve elasticity from root to tip. Targeting weakened and brittle strands, the silky formula helps to rebuild the hair’s internal structure to make it more resistant to breakage, whilst a blend of lipids creates a smooth and shiny surface. The shampoo gently lifts away the build-up of dirt, impurities and excess oil from the scalp to leave locks fresh, clean and strong.