‘Disulphide bonds are one of the strongest naturally-occurring bonds in nature.’ The protein structures of the hair shaft are held together by chemical bonds called disulphide and hydrogen bonds.

While the curliness (or straightness) of your hair depends on the shape of the follicle, it’s the disulphide bonds that keep the hair in the shape it was formed, and they can only be altered by perming or relaxing.

Disulphide bonds also give your hair its elasticity and strength. Hydrogen bonds, on the other hand, are easily broken by the application of water and can be temporarily reset with heat until they become wet again (either from washing or humidity).