Which hair bond type is most affected by moisture and temperature changes?

• A. Hydrogen bonds
• B. Disulfide bonds
• C. Salt bonds
• D. Peptide bonds

Answer: (D)

Moisture and heat mainly disrupt hydrogen bonds in hair. These bonds are the weakest links between keratin strands, so water molecules readily break them, causing hair to swell when wet and to reform its shape as it dries or is heated. This reversible breaking and reforming under different humidity and temperature conditions explains why hair takes on different shapes with styling or environmental changes. Disulfide bonds are strong covalent links and require chemical methods to break; salt bonds depend largely on pH in addition to moisture but aren’t as immediately affected by temperature alone; peptide bonds form the stable backbone of keratin and aren’t altered by ordinary moisture or heat.