Hair that is treated with hydroxide relaxers must not be treated with

• A. Thio relaxers
• B. Hydrogen peroxide
• C. Ammonia
• D. Coloring agents

Answer: (A)

The main idea here is chemical compatibility: strong hair relaxers that use hydroxide raise the pH to break disulfide bonds, preparing the hair to straighten. Thioglycolate-based reducing agents, used in thio relaxers, work by reducing those same bonds but through a different chemical pathway. When a hair that’s already been treated with a hydroxide relaxer encounters a thio-based relaxer, the two chems clash, leading to uncontrolled bond breaking and a severe structural breakdown of the hair. This can cause extreme damage, severe breakage, and uneven texture. That mismatch is why hair treated with hydroxide relaxers should not be treated with thio relaxers.

Hydrogen peroxide, ammonia, and coloring agents don’t involve this same direct, destructive interaction with hydroxide-relaxed hair when used in typical sequences, so they aren’t ruled out by the same incompatibility.