Dr. Haidi's Picks: Olaplex, K18 & Worth-It Buys

They work on different mechanisms — Olaplex rebuilds broken disulfide bonds, K18 uses a peptide to repair the keratin chain itself. Many people use both at different points in their routine rather than choosing one over the other permanently.

Most tap water carries enough metal content to affect colored hair over time, even when it doesn't look or feel unusually hard. If color fades faster than expected, this is worth trying before assuming the dye itself is the problem.

In each case, the formula is solving a specific, named problem — broken bonds, metal buildup, weakened roots, pigmentation — rather than being a general-purpose version of the category. That's usually where the price difference actually shows up in results.