Perhaps yogurt works by surface smoothing/coating of curls. I do not use it as a protein treatment but rather bc it is known for sleeking curls. whether this is due to surface coating, lactic acid or some other reason I do not know but it makes a noticeable difference in the quality and manageability of natural curls.
So remember, not everything has to be absorbed inside the hair to "work" Some treatments like ceramides work by coating the outside of cuticles as opposed to necessarily penetrating the inner shaft. A two phase approach is often useful for some hair types. Small molecules to penetrate inside the shaft and larger molecules like lawson ( henna) ceramide oils as surface treatments.
Another important fact is that other products are meant to seal the shaft as in the TWO stage approach of moisturizing and sealing. The moisture enters inside the shaft while the job of a sealant is to sit on the surface to trap and seal the moisture inside.
This is part of the debate about whether mineral oil is bad. Some claim it is bad because it does not necessarily go inside the hair shaft. If it is used always on wet hair, it is the sealant in the moisturizing and sealing process. So it would not need to go in the shaft for that. The problem with that is if you try to use it alone on dry hair without doing the moisturizing step first with a moisturizing product.
So remember everything does not have to go inside the shaft. Some great products do their job by working on the surface like hennas, ceramide oils, and sealing oils that go on after moisturizing. Another product that would go in this category is waxes that are used to tame heavy afro hair and gels which are used similarly more on Euro hair.
Edited by LadyAradia - Jan 30 2014 at 12:24pm