The right hair conditioner can make your hair glossy and bouncy, but the wrong one can instantly make it lifeless and lank. What’s in them that make them so different?
pH and hair
The most important thing about hair conditioner is that it’s acidic (pH < 7). Hair is made up of three major layers – the innermost medulla, the cortex where hair dye sits, and the cuticle, which is made up of overlapping flat cells like fish scales. These are supposed to lie down flat in a smooth, shiny layer, which is held together by forces called hydrogen bonding (I promise you it won’t get much more complex than this!).
(More info on pH in my post almost exactly a year ago here!)
Humectants - Humectants are in skincare too – they attract water to the hair and keep it there. Examples include panthenol, glycerols. If your hair is prone to frizziness when humid, a conditioner with lots of these might make it worse.
Silicones - These coat the hair in a thin, glossy film which is slippery and lubricated. Silicones also help protect the hair from heat styling damage. They can weigh down fine hair, cause build-up, and straighten natural waves and curls, but some people (me included!) love the effect they have on hair! Dimethicone,dimethiconol, amodimethicone and cyclomethicone are all silicones.
Proteins - These are often touted to “repair” the hair, and some might penetrate the cuticle, a little bit – but these claims are usually overblown, and the repair is never permanent. They will often form a protective coating over the damaged hair though, but there are many other ingredients which do this, without the hefty price tag that protein-containing conditioners often have. Examples include hydrolysed keratin and silk proteins.