Your addiction: Colouring your style to within an inch of its life.

The damage: Your hair has a protective surface shield, and this chemical- and water-resistant layer prevents damage and maintains the hair's moisture balance, explains Alison Roughley, senior scientist at Procter & Gamble. "When hair is coloured, this layer is lost, making strands more porous and, consequently, drier," she adds. "During colouring, the cuticle is temporarily lifted away to allow the colour molecules to enter. But, with consecutive colouring, it can become more difficult for the cuticle to flatten properly, and lessens its ability to hold onto the pigment." Incorrect colour application and over-processing will cause structural erosion to the hair. "Powder lightener [bleach] can cause the most damage, and semi-permanents may make your hair look washed out," remarks Brad Ngata of Brad Ngata Hair Direction..

Your solution: "Colour needs to be applied correctly, so consulting a reputable colourist is a wise investment," emphasises Ngata. At home, use products designed for coloured hair. "For blondes, I love KMS California Colorvitality Blonde Shampoo, $23.95, which is designed to cancel out unwanted brassy tones," he adds.

You need:
Above, from left: Redken Colour Extend Conditioner, $23.95; KMS California Colorvitality Blonde Treatment, $17.50; Kérastase Soleil Bain Après-Soleil Anti-Photodamage Repairing Shampoo for Color-Treated Hair, $31.50; L'Oréal Professionnel série expert Lumino Contrast Radiance Masque for Highlighted Hair, $25.95.