A relaxer is a chemical product used to straighten curly or wavy hair. It works by breaking down the protein structure of the hair, allowing it to be reshaped into a straighter form. Relaxers are commonly used in hair salons and can be applied at home, but they require careful application to avoid damage. There are two main types of relaxers: lye and no-lye. Lye relaxers contain sodium hydroxide, while no-lye relaxers use calcium hydroxide or guanidine hydroxide. Both types can effectively straighten hair, but they have different pH levels and may affect hair health differently. Regular maintenance is necessary to keep hair healthy after using a relaxer.