The Marketing Story
The marketing materials for these products were the next step in the investigation. Nexxus says that after one use of the system (shampoo, conditioner, leave-in creme, and heat protection spray), 92% of your split ends would be repaired. This is such an exact number, which can be quite convincing when used in advertising, but I could find no data published anywhere to support this. There was no description of how they defined, ascertained, or quantified repair, but they did show a nifty video of a damaged hair strand coming back together. Their marketing materials use words such as "binding" and "healing" and "nourishing" to describe the effects of their products on damaged hair.
The thing that most interested me was a brief video in which they provide instructions for the proper use of the product. After shampooing, conditioning, applying leave-in cream, and using the thermal protector spray, the consumer is directed to blow dry her hair using a round brush and to follow up with a flat iron. The celebrity stylist assures us that the repair and strengthening results will be instantaneous and will last two to three months or longer with continued use of the product.
Ding, ding, ding! With this last piece of information, my glimmer of suspicion transformed into a raging hypothesis. (Is there such a thing as a raging hypothesis? How about a really excited, bouncing up and down hypothesis? I know, I am a science nerd.)
The Proposed Mechanism
The combination of several aldehydes (hexylcinnamal, butylphenyl methylpropional), a formaldehyde-donor preservative (DMDM hydantoin), a drop of base (NaOH), a few keratin amino acids, and a recommendation to use high heat (flat iron) all indicate to me that this hair system could be exploiting the same chemical mechanism used in the Brazilian keratin straightening treatments. (reference this previous piece for more detailed chemical information about Brazilian Keratin Treatments) The general idea is that aldehydes react with amino acid side chains of hair keratin and also with the hydrolyzed keratin amino acids in the product. This enables them to effectively form bridges between the split pieces of hair and to bond new keratin onto the surface of the hair. These bridges could "glue" the hair strand back together and also give it a smoother, glossier appearance.
If this is indeed the mechanism being utilized, it is important to note that while the effect may be cosmetically pleasing and somewhat sturdy, the split ends of the hair are bound in a manner similar to a torn piece of paper that has been glued back together. It will hold and may look nice, but the weakness or flaw is still there. The crosslinked bridges that are formed by the aldehydes are not permanent and usually last two or three months.
The scientists at Alberto Culver (parent company to Nexxus) have developed and cleverly marketed a very interesting new product that promises to repair and prevent split ends. Traditional moisturizing conditioners and protein treatments provide topical smoothing for hair and can fill in some gaps in the cuticle and hair shaft. However, none have been able to bind together pieces of a hair that has split into pieces. Analysis of the product ingredients leads me to believe that this product may in fact be binding the pieces of hair together via aldehyde reactions with keratin amino acids. If so, this is a very creative application of this technology.
Without direct confirmation from someone at Alberto Culver (soon to be Unilever), I am purely speculating about the chemical mechanism of the Pro-Mend products. I did consult the literature and patent space though, and happened across at least two patents that indicate that my hypothesis is plausible. It would be wonderful to learn the exact truth, but in this competitive market, it is best to keep one's cards close to one's chest.
The important things to note about this product are that it does seem to be an effective conditioning system, and many have reported an improvement in the appearance and strength of their hair. However, it does contain aldehydes and the makers do recommend using high heat on your hair for best results—something which many of us tend to avoid due to concerns of thermal damage. Finally, while the Pro-Mend system may chemically glue split ends back together temporarily, there is just no replacement for regular haircuts.