Curly hair, and African-American hair in particular, can be dry. Products aimed for the latter used to contain not only mineral oil, but petrolatum, lanolin and sometimes vegetable oils. Petrolatum is greasy and contains wax; lanolin is a greasy, sticky wax and both can be hard to remove from hair without clarifying.
FIXING FRAGILE COILS
MINERAL OIL BENEFITS FOR HAIR
Mineral oil can help to rehydrate dry hair. If a small amount (small drops) is evenly applied to very damp or fairly wet hair for curly girls, the oil can help keep moisture in the hair by slowing down moisture evaporation and allow good curl retention. It also slows, but does not seal out, access to the hair by atmospheric moisture, helping to prevent frizz. For hair with a good moisture level, it can be used on dry hair to help maintain that level.
There is no reason why mineral oil should not help to keep moisture in even severely damaged hair caused by chemical processing, or heat styling, when used on very damp or wet hair. Damaged hair can be very dry. The cuticles, having been compromised by the damage, are unable to keep moisture in the hair well, even if they are closed with an acidic rinse. Mineral oil cannot repair damage. No product can do that. It can help keep moisture in the hair, making it feel softer, aid in detangling and add shine.
*for more info on the hydrophobic properties of mineral oil and its ability to effectively seal moisture into the hair (compared with coconut oil), click HERE*
Mineral oil is not sticky. Used in small amounts it is not greasy either, which can result in hair looking stringy. Mineral oil can reduce and eliminate tangles and is antistatic. It can work effectively on hair that has been conditioned or unconditioned. It works most effectively when hair does not have a lot of conditioner on it at one time, or residue (build-up), and when it is not combined with other oils. Reapplication between washes is usually not necessary. The hair can be moisturized and sealed enough, to not feel or look dry.
Mineral oil is known to seal moisture into skin more effectively, than vegetable oils or silicones. It is also known in the cosmetic industry for: ease of spreading; shine; and slip thereby reducing friction.
The best choice of mineral oil is one with the least ingredients because it is the mineral oil itself that is the effective ingredient wanted. Other ingredients may cause build-up or cause hair to look greasy. Baby oil is often sold with just two ingredients, paraffinum liquidum (mineral oil), and fragrance. Sometimes tocopheral actetate (vitamin E) is listed. It is used as a stabilizer for cosmetic mineral oil and is often not listed.
USP/BP mineral oil is safe, classified as natural, can be biodegradable, and by using it in such small quantities, it is managing a limited resource very well.
References 1. “Petrolatum/Petroleum Jelly” http://cosmeticsandskin.com/bcb/petrolatum.php