Encyclopedia · oil or butter
Mineral oil
A cheap, non-penetrating hydrocarbon oil that coats hair for shine and slip but, unlike coconut oil, did not protect against protein loss in lab tests.
What it is
A refined petroleum hydrocarbon, common in Indian hair oils and many serums because it is inexpensive and does not feel greasy.
How it works
Mineral oil did not penetrate the hair shaft in an ion-imaging study, unlike coconut oil, probably because of its non-polar nature. Ruetsch 2001 It acts as a surface film.
What the studies show
- Coconut oil penetrated hair cross-sections and mineral oil did not. Ruetsch 2001
- Mineral and sunflower oil did not reduce protein loss, while coconut oil did (Marico study). Rele 2003
- Coconut oil raised the tensile strength of twisted fibres, while mineral oil did not differ from washing alone (Marico). Kaushik 2021
- All three studies were run by or with a coconut-oil marketer, a conflict of interest favouring coconut oil.
How it's used in studies
Pre- and post-wash hair oiling and overnight oil treatments. Kaushik 2021
Side effects and safety
Cosmetic-grade mineral oil is not a prescription ingredient. Heavy application may weigh hair down and need shampooing out. We did not verify claims about scalp pore-clogging.
Bottom line
A fine, inexpensive sealant for dryness and frizz on the lengths, but do not expect internal strengthening. For protection against protein loss the data point to coconut oil. The "mineral oil is toxic" myth has no support in the hair literature we found. We are moderately sure about the penetration finding and unsure overall. Independent (non-Marico) replications are lacking.
Studies 3
Ruetsch SB et al. SIMS investigation of penetration of coconut and mineral oils into human hair fibers. J Cosmet Sci. 2001
Tested: coconut oil vs mineral oil
Result: Coconut oil penetrated the hair fibre; mineral oil did not.
Read the study ↗Rele AS, Mohile RB. Effect of mineral oil, sunflower oil, and coconut oil on prevention of hair damage. J Cosmet Sci. 2003
Tested: mineral, sunflower and coconut oil
Result: Mineral oil did not reduce protein loss from combing in either undamaged or damaged hair; coconut oil did.
Read the study ↗Kaushik V et al. Single hair fiber assessment techniques to discriminate between mineral oil and coconut oil. J Cosmet Dermatol. 2021
Tested: coconut oil vs mineral oil across washes
Result: Coconut oil, not mineral oil, strengthened twisted fibres across washes.
Read the study ↗Related
- Coconut oilThe best-studied hair oil; in lab work it cut protein loss and fatigue damage when used before washing, but almost all studies come from coconut-oil sellers.
- Sunflower seed oilIn the classic Marico study sunflower oil did nothing for protein loss, though later work suggests oils of its type can penetrate hair.
- DimethiconeThe standard hair silicone, a water-insoluble oil that coats the fibre for slip, shine and friction control without repairing anything.
- Oils and hairOils coat hair and some enter it, which can cut damage from washing, but they do not repair split ends or add moisture.