I admit I've never formulated for African hair types, so I present to you what I have found in my research. I would love to hear from any readers who have this hair type so we can add more information to this post.
ultra-curliness, and the follicle size tends to be quite thick. It tends to contain much lower levels of cysteic acid than other hair types. It is more hydrophilic (or water loving) with a negative charge. In addition, it tends to have lower levels of bonded lipids on the hair shaft, which explains why this hair type tends to love oils!
African type hair is much weaker than other hair types due to the kinks in the hair shaft - more kinks equal more opportunities for breakage - and is less resistant to strain on hair and scalp. It can take as little as 33 grams of strain to break an African hair type while wet (about 43 grams for Caucasian and 63 grams for Asian hair, about a 100 grams for these hair types dry), which means any slight pulling can cause hair loss! The elasticity of African is hair very limited - whereas Caucasian hair types can take average pulling and Asian above average pulling when wet - African hair can break when even more than slightly humid!
African hair tends to be very dry, but this does not mean we want to add humectants to our products because too much water can lead to that increase in breakage. So we have to add moisture in other ways, through oils and by sealing in what's there through silicones.
The cuticle is different in African hair - whereas Caucasian hair might have 4 to 7 layers of cuticle, and Asian hair 11 plus, African hair has about 7 to 11 layers of cuticle. Fewer layers means more alterations by chemical treatments like dyes, straightening, or perming, so African hair is about the average of chemical absorption with regards to cuticle (with Caucasian being lower, Asian being higher). But flatter hair strands absorb more chemicals, so in the end African hair is probably more accepting of chemical treatments than other hair types.
As for hair care products, it's recommended that African hair types use intense conditioners filled with oils and very few (if any) humectants. Because water is not your friend - humidity can increase breakage dramatically - you want to use things like silicones to prevent your hair shaft from absorbing it. Oils are your friend, so oiling your hair with like avocado, babassu, and coconut will increase the hydrophobic (water hating) nature of your hair to keep that nasty water out!
Sebum is your friend, so you want to use very gentle, daily use shampoos at pH 6.5 or so on your hair filled with conditioning agents and silicones because we don't want to remove all the sebum and we want to seal out the water. (It's uncommon for this hair type to be really oily!) You want to use the most gentle surfactants suitable for dry hair at very low levels, and you don't want to wash your hair daily. Please for the love of all that is good do not use cold process (alkaline) shampoos or shampoo bars on your hair - this can increase the breakage of your hair!
We'll be formulating some very nice daily use shampoos and intense conditioners in the coming weeks suitable for the African hair type.
I'd suggest getting some cetrimonium chloride in your conditioners at up to 5% to increase the combability of your hair and increase detangling, which will also increase softness and aid in removal of styling products. (Although combing is really not your friend, so don't do it often!) Incroquat CR is also a good choice for softening. Cetrimonium bromide will penetrate the hair shaft to moisturize from within, and BTMS-50 is always a good choice for lubricating and conditioning all hair types.
Leave in conditioners are great for African hair types, and some can even use daily use type conditioners as leave in conditioners. Make sure you are formulating with lots of oils and few humectants, and ensure you are using styling products with low levels of alcohol (which can dry out your hair and make it easier to break!)
Although some protein is great for African hair, you want to limit your usage of it until you see how your hair responds. (Page 607, Handbook of Cosmetic Science & Technology notes that the addition of protein hydrolysates - hydrolyzed proteins - is "highly recommended", but I've seen some people say they don't like them.) Something like Phytokeratin - a combination of low and high molecular weight proteins - is probably your best choice because you'll get the film forming benefits of the oat protein with the moisturization provided by the corn or soy protein. If you want to use proteins in your products, save it for the conditioners or styling products and use it at about 2% - 1% something like silk, 1% something like oat so there's a balance of penetrating vs. non-penetrating proteins.
Panthenol is also a great ingredient for African hair, despite the fact it can behave as a humectant. At least 2% pathenol in a conditioner can help bring moisture into your hair and form a film to keep too much moisture out! It can increase the elasticity of your hair strand, and we know that's really important for African hair!
I've written up a post with some great research I found about African hair types. Click here to see it!