why is there residual smell after using the smooth over treatment?Updated 9 months ago
we have had very few reports of a post-treatment odor. this issue did not arise in our own testing of the product, so we are investigating what variables may be interacting with our formulation to produce an odor in rare cases. we have limited information at this time, but our working hypothesis is that the product may be interacting with compounds in water of varying quality or other products that are used in conjunction with smooth over treatment, such as color or non-amika shampoos.
recall that the product works by adding a molecule called glyoxylic acid to the hair, which, upon heating, forms a polymer layer that seals the cuticle and forms an “umbrella” that resists humidity and frizz. polymer formation of this kind is called “plasticization”. it’s kind of like wrapping the hair cuticle in saran wrap temporarily to protect from frizz-causing humidity. additionally, glyoxylic acid works within the hair to restructure bonds in the keratin (mainly weaker salt, hydrogen and van der waals bonds). this chemistry involves potential reactivity with some sulfur-containing amino acids (aka protein building blocks) residing on the termini of the keratin. under conditions in which too much product is used, or if there are other chemical catalysts present in the hair (e.g. metal ions and contaminants such as chlorine, magnesium, and sulfur from water), these reactions may result in the release of sulfur-containing compounds. sulfur-containing compounds have a smell often described as “rotten egg”. some residual smell is to be expected for the first few washes because when the hair becomes wet, this can volatilize some of these sulfur-containing compounds. volatilization means driving molecules into the air via evaporation, which means these molecules will be detected by your nose. this volatilization is akin to dropping a water droplet into a glass of whiskey to enhance the aromas – similarly, wetting the hair post-treatment may make the residual smell stronger.