Why Sulfates Are Not Actually Damaging Your Hair

The level of copper in water is typically quite low, but that small amount is still enough to create long-term hair color issues. Look for shampoo formulas that contain histidine, an amino acid that both removes impurities from inside the hair shaft and strengthens the strand.

"Histidine will bind and block the copper that's already in the hair, deactivating it from changing the color over time," explained Wilkerson. "It's good to use it several cycles before you color your hair again." That way, the histidine will be inside your strands, fortifying them against damage and shade fade. Read on to shop shampoos with histidine!