On August 13th, 2018 we learned about

Conditioner makes hair manageable by coating cuticles in protective, fatty molecules

Between weekly swim lessons, ballet classes, misplaced food and the occasional lice infestation, my kids’ hair has taken a fair amount of abuse in the last few years. Since my daughter still hasn’t taken up my offer for a buzz-cut, there’s always a lot of griping about snarls and tangles when she needs to brush her hair. Aside from cutting back on exposure to heat and other activities that may dry hair out, the main tool to smooth things over has of course been hair conditioner. The white goop has seemed rather miraculous at times, removing tangles faster than even an hour of brushing. This naturally raised a few questions from my daughter— can conditioner replace brushing out snarls (no), and what exactly is conditioner doing in the first place?

Hair shaped by its outermost structures

To make sense of hair conditioner’s ability to make hair seem smoother and shinier, you need to first think about what a hair looks like on microscopic level. Hair is made up of the same class of proteins, called keratin, that make up your fingernails, rhinos’ horns and birds’ feathers. Obviously your hair doesn’t feel like these other bits of anatomy, which is largely thanks to the structure of a hair. At a hair’s core is medulla, which is then covered by a cortex, which is in turn covered by an outer, flaky-looking layer called the epicuticle. It should be noted that none of these structures are made of living cells, which means that their “health” is a non-factor in how your hair behaves. So instead of helping hair repair itself from damage, hair products like conditioner instead help patch things up from the outside.

The epicuticle is the key to a lot of your hair’s behavior and appearance. It’s a layer of overlapping flakes of protein, arranged a little like somewhat uneven shingles on a house. Ideally, your scalp produces the right amount of an oil called sebum to help coat and arrange the pieces of epicuticle so that they lay as flush along the shaft of the hair as possible, creating something like a single, uninterrupted surface. However, when your hair becomes dried out by something like heat from a blow dryer, the epicuticle flakes start to separate, turning the hair into a rough surface that is better at holding static electricity for frizzies, getting hooked on other hairs for tangles, and generally looking duller overall.

How conditioners control the epicuticles

So to make this frizzy, tangled hair play nice, conditioner’s main purpose is to get the epicuticle flakes to lay down as smoothly as possible. To start, a small amount of acid in the conditioner will break up some of the charge between each separated flake, helping them fall against each other more tightly. These are followed up by a series of lubricating ingredients that essentially coat each hair in a temporary sheath of protective oil. Ingredients like quaternary ammonium salts are attracted to the negatively-charged keratins in the epicuticle, followed by fatty alcohols like cetyl alcohol a handful of silicones to round things out. These silicones not only cap off the protective matrix of fatty molecules, but also add a fair amount of shine, as if each hair was laminated in vitamin E-infused plastic. This may sound like a lot of chemistry on your head, which it is, but it’s not really anything all that exotic or worrisome. If you’ve ever made your own salad dressing or mayonnaise, you could probably handle whipping up a batch of conditioner in your own kitchen.

So what about the aforementioned vitamin E? Or any other cool, fancy or compelling ingredients that your hair products might contain? There’s a good chance that they’re their for your nose and imagination more than your hair. Since the keratin in your hair isn’t alive, coating it with oily, fatty ingredients is really the best that you can aim for. Beyond that, ingredients that give a conditioner a nice smell, color and texture in your hand is all optional. Products that promise ‘intense deep conditioning’ or other impressive claims probably can’t do more than an application of coconut oil. For smooth, shiny hair, it’s really just a matter of getting just the right amount of grease to keep your epicuticles in line.


Bonus: So what’s shampoo doing?

Ignoring all the scents and gimmicks packed into each bottle, shampoos essentially work like any other soap out there. They’re full of “surfacant” molecules that have one hydrophillic end and one lipophillic end. As you scrub your head, the Lipophillic end of these molecules grabs dirt, oils and fats off your hair. When you rinse, the hydrophillic ends grab the passing water molecules, only to be pulled off your head and down the drain. They take the dirt and oil with them in the process, leaving your hair clean and… ready to be re-oiled by your conditioner.

Source: How does hair conditioner work? by Krystnell A. Storr , Science Line