in this post: I have a question... which oils would you please suggest for hair leave-in conditioners? I see you've mentioned coconut, camellia, sea buckthorn, jojoba, avocado in some posts, but is there a post that discusses recommended oils for different hair types (with reference to their properties)?
There doesn't tend to be a huge difference in using oils on our hair the way there is for oils on our skin. You'll see me write about something like sunflower oil as containing a lot of linoleic acid, so it's good for skin that needs some repair or something like olive oil containing a lot of oleic acid, so it's good for skin that needs moisturizing and softening, and we can extrapolate from that information that someone with wind chapped skin, for instance, could probably benefit from something like sunflower oil because there's been some damage to the skin's barrier or that someone who has callouses could benefit from olive oil for the softening. But there isn't that kind of information about hair.
When it comes to oils and butters in hair care products, for the most part you're really choosing them for their ability to moisturize your scalp and coat the hair strand. Which means you can choose the butter or oil you like - cocoa butter, shea butter, sunflower oil, and so on - and it really won't make a massive difference to the actual hair strand. Most fatty acid molecules are simply too big to penetrate into the hair shaft, so most of it will rinse out when you rinse the conditioner out of your hair. If you're using them in a leave in conditioner, you can choose pretty much anything you want if you're looking to coat the hair strand.
Coconut oil has had a lot of studies done about it, and they've shown that lauric acid has an affinity for hair proteins and the molecules are small enough to penetrate the hair strand. (Click here for a recipe...) Virgin coconut oil offers the same features, and it smells wonderfully of coconuts! Jojoba oil is interesting in that it penetrates your hair follicle, so it will offer some cleansing and moisturizing of your scalp. Olive oil will help your scalp, but it's not going to penetrate your hair strand. Sea buckthorn oil might be good for your scalp, but I haven't found evidence it works well for your hair, and avocado oil is supposed to be great for itchy scalps - no doubt thanks to the oleic acid - but there's nothing saying it does more for your hair than other oils. (I know there's talk about argan oil being good for our hair, but I can't find anything to back up that claim.)
Lauric acid is a smaller molecule than something like stearic acid, oleic acid, linoleic acid, and so on, which is part of the reason it can penetrate the hair shaft. If you use another oil that contains lauric acid - like babassu oil or murumuru butter - you might get some of the same benefits as using coconut oil.
It seems that when people are looking to use oils to moisturize their hair, they're really looking for more conditioning or more water retention, and neither of these goals is accomplished well by including more oils in hair care products. If you have really dry hair, you're better off incorporating more humectants into your products to draw water from the atmosphere to your hair. Adding some glycerin, honeyquat (which conditions as well), sorbitol, or another humectant to your product will increase the moisturization level of the product better than adding an oil.
If you are looking for more conditioning, adding more cationic quaternary compound - like Incroquat BTMS-50, Incroquat BTMS-25, Incroquat CR, cetrimonium bromide, behentrimonium methosulfate, and so on - will increase the conditioning of the product. Adding a fatty alcohol at up to 50% of the conditioning agent - something like cetyl alcohol, cetearyl alcohol, behenyl alcohol - will boost the substantivity of the product.
If you really are looking to include a ton of oils in your products, then I've included some links below that might help!
So the short answer for Sarah's question is that if you want to add an oil to a leave in conditioner to benefit your hair strand, I'd go for coconut oil or another oil with lauric acid. If you want to add an oil to a leave in conditioner to help your scalp, then you have quite a few to choose from. Go for something that you like and have around the house because there isn't a big difference in carrier and exotic oils when it comes to moisturizing your scalp or coating your hair strand.
I know there will be people who disagree with me, and that's great. Send me along the links for the information you provide and I'll read them!
Adding slip to hair care products with fatty alcohols
Conditioners: Humectants and frizz
Adding slip to conditioners with oils and butters
Hair care section of the blog
Emollients - oils, butters & esters - section of the blog
E-mail question: Using oils in our hair care products