Oils such as coconut oil are known to penetrate hair while others such as sunflower oil simply form a coating on the top of hair. I have noticed a trend of women choosing penetrating oils over those that do not and therefore the question arises, are penetrating oils really better for your hair?
The Advantage of Penetrating Oils
Penetrating oils are good especially during the washing stage of hair. Coconut oil applied to dry hair before washing (allowing a few hours for the oil to penetrate) will prevent the hair from taking up a lot of water. This action helps hair control its expansion and using coconut after the wash can in addition prevent minor breakage and protein loss which comes from cuticle chipping. The analogy I usually give is a rubber band, how many times can you stretch it before it eventually breaks? During washing, hair takes up and releases water which causes the cuticle to lift slightly and then contract back down. Repeat this process several times and eventually some of the cuticle will chip. This is known as hygral fatigue and penetrating oils such as coconut oil are known to prevent this type of damage (Journal of Cosmetic Science pg 169-184,2001).
The Advantage of Coating Oils (i.e non penetrating)
Now, when it comes to moisture, oils that do not penetrate hair are really superior. Oils that can form a film over hair can effectively create a barrier to prevent water that has been taken up by the hair from evaporating quickly. This is the reason why a coating oil like mineral oil which forms a thin even film over the hair is much more effective as a ‘sealant’ than coconut oil ( International Journal of Cosmetic Science, pg135-145, 2007). Penetrating oils naturally will get under the cuticle and therefore do not create an even barrier. Therefore oils which tend to coat hair, in the same way natural sebum does are the better moisturisers.
Ladies, do you use both penetrating and non-penetrating oils? What is your favorite oil to use?