Once in the cortex, the waving solution breaks the disulfide bonds through a chemical reaction called

• A. Oxidation
• B. Reduction
• C. Hydrolysis
• D. Condensation

Answer: (B)

Breaking disulfide bonds in the cortex during a perm occurs by reduction. The waving lotion provides a reducing agent that donates electrons to the sulfur-sulfur cross-links in keratin, turning the disulfide bonds (-S-S-) into two sulfhydryl groups (-SH). This loosens the hair’s structure so it can be reshaped around rods. After molding, a neutralizer oxidizes the thiol groups back into new disulfide bonds, locking in the new shape. So reduction is the correct term because it specifically involves breaking those cross-links by gaining electrons, rather than oxidation (which would rebuild bonds), hydrolysis, or condensation.