Disulfide bonds are in all three main parts of the hair:
• Cuticle
• Cortex
• Medulla (if the hair has one)
Most people think about how Keratin (proteins) make up the hair, forming polypeptide bonds (long chains) that are kept in alignment by hydrogen, salt and disulfide bonds.
The overall internal structure resembles ladders that have been twisted into a shape resembling a multi-fiber cable called microfibrils. These then combine to form macrofibrils which are contained in the cortex. These “cables” stay in alignment, resisting twisting and bending, as a result of disulfide bonds. They are held together in the cortex with a microcellular cement that also contains an abundance of disulfide bonds.
All hair contains millions of disulfide bonds which give the hair its structure, strength and stability. When all the bonds, especially the disulfide bonds, are intact and in alignment, you have healthy, beautiful, shiny, touchable hair. When disulfide bonds are broken, it results in damage.
Hair is damaged daily. Split ends, frizz, lackluster Color, thinning and dryness can all be related to broken disulfide bonds.
• Flat irons, curling irons, and blow dryers all cause damage due to the high levels of heat being used.
• Mechanical damage such as brushing, friction, tugging and pulling on wet hair affect the bonds.
• UV damage from the sun, humidity, extreme hot/cold weather conditioners, pollution, etc. all have a negative impact on the hair’s bonds.
• Chemical services can also cause damage. These services include Color, Lighteners, Perms, Relaxers, Keratin Treatments, and Japanese Straighteners/Thermal Reconditioners.
The chemicals and/or thermal tools being used react with the disulfide bonds breaking them and causing protein loss, leaving behind damaged hair. When damage occurs, it affects the disulfide bonds throughout the entire hair fiber.
