Mineral oil is vilified on many natural hair care sites but I often wondered where is the proof? The reasons given range from the simplest, ‘It is terrible for your hair,’ to more detailed reasoning such as robbing your hair of moisture or coating your hair in a film etc.
Well, the science is here! Mineral oil does not penetrate into the cortex of hair (Journal of Cosmetic Science pg 169-184,2001). This is because the oil does not have an affinity for protein (meaning it is not attracted to protein).
It also prevents water from getting into the hair shaft and may I quickly add that this is NOT necessarily A BAD THING.
Hair that takes up a lot of water and then loses it again can undergo what is known as ‘hygral fatigue’.
The hair actually becomes weaker due to the swelling and de-swelling (Analogy – how many times can you stretch a rubber band until it breaks?). Damage can be sustained to the cuticle and cortex which becomes an even greater problem during combing or manipulation.
Therefore, mineral oil is not entirely bad (offering some protection against porosity) but certainly is not great (not penetrating the cortex and preventing water entry to parched hair). This is especially true if you compare it to the simply wonderful all singing, all dancing coconut oil.