A Dermatologist’s Guide to Hair Oils

Let's understand what oil to use for what, and what the potential dangers are of using some of these incorrectly.

So many types, so many claim to fames, what is true?

Hair oils have exploded in the last decade, but have been used for years in their native subcontinents, coconut oil in India, tea tree oil in Australia, Argan oil in Morocco, and Olive oil in the Mediterranean just to name a few. And then came along essential oils.

Let's understand what oil to use for what, and what the potential dangers are of using some of these incorrectly.

Coconut Oil

Coconut oil has been used for years in Africa and Asia, and has been heavily studied in India where it is used widely. It is made up of medium-chain triglycerides (MCT) which are unique in that when ingested they go straight to your liver for a quick source of energy or to be made into ketones.

This oil penetrates hair deeply, used as a prewash treatment will prevent protein loss from the hair fiber during combing and from ultraviolet radiation from the sun1. It hydrates and strengthens hair, making strands less prone to break2. Because this oil is so thick it can clog pores, so avoid applying directly to the scalp or you make get an irritating form of scalp acne: folliculitis3.

Tea Tree Oil

Tea Tree Oil comes from Melaleuca alternifolia, a plant found in the coast of northeast Australia. It is very popular in cosmetics due to its anti-viral, anti-bacterial, and anti-fungal properties.

Use this oil to help get through any thick rash on the scalp, like heavy dandruff, of scaly psoriasis. It reduces the itch and greasiness that can come with these conditions. Do not use the oil on healthy hair or healthy scalp because it can be very irritating4. An alternative natural product that also helps with dandruff and psoriasis but won't irritate or harm healthy scalp is honey. Honey also contains fructose, glucose, proteins, amino acids, vitamins, enzymes and minerals that nourish hair and scalp.

Argan Oil

This oil comes from the fruit of the Argania Spinosa tree, found in southwest Morocco and Algeria. It is rich in linoleum acid, vitamin E, oleic acid, and is intensely hydrating.

This oil adds significant shine and lubricates hair. It is great for hair damaged from harsh chemicals like bleaching or keratin treatments since it reduces protein loss, strengthens, and protects the hair from further damage. There have been some rare reported allergies so if you are someone who tends to have a lot of allergies you may want to be cautious.

Olive Oil

Olive oil is a liquid fat extracted from olives (Olea europaea) and have been used in the Mediterranean for thousands of years.

This is great for softening the hair and adds a luminous shine while hydrating strands. It is an ingredient used in labs to help grow the Malassezia fungus, so if you are prone to fungal infections or dandruff this may make it worse. Also be wary of using on babies, as it has been shown to decrease the thickness and strengths of the stratum corneum, which is the top layer of skin. It is also known as a skin irritant so avoid using directly on the scalp5.

Castor Oil

Castor Oil comes from the seeds of the Ricinus communis plant. It has been touted as a hair growth oil, but these claims have no supporting evidence unlike other hair-growing oils (see below).

What castor oil does do due to its very thick, viscous consistency, is make hair appear thicker, but has no influence on actual growth. So it is still great to use for thinning brows. It does soften hair and adds considerable shine and hydration. There has been one case of irreversible hair felting due to castor oil, which lead to the woman who applied it to her hair to have to cut the entire area that was affected, so to be safe just use on eyebrows6.

Lavendar Oil, Pepperment Oil, Rosemary Oil

These oils which come from various parts of Europe have been scientifically studied for their ability to grow hair.

Lavender oil influences the levels of sex hormones, leading to increased hair growth on scalp, preventing hair loss on scalp7, and counterintuitively, reduces unwanted facial hair in women8. This makes sense when you consider male hormones lead to balding and increased facial hair.

Peppermint oil is typically used as a gastric stimulant but has been shown to help with hair growth, increasing the number of hair follicles and the depth of follicles. It is believed to speed up the Anagen stage of the hair cycle, which is the stage where hair grows9.

Rosemary Oil enhances blood flow when applied to skin or scalp. This is similar to how Rogaine (Minoxidil) works, in fact a study compared the two side by side and found that after 6 months both significantly increased hair count, with no statistical difference in the rosemary oil group compared to the Minoxidil group. Notably, the rosemary oil group complained less about itch than the minoxidil group. So this may be a great therapy for androgenic, or hormone-related hair loss.

References

Rele AS, Mohile RB. Effect of mineral oil, sunflower oil, and coconut oil on prevention of hair damage. J Cosmet Sci. 2003 Mar-Apr;54(2):175-92. PMID: 12715094.

Wallace TC. Health Effects of Coconut Oil-A Narrative Review of Current Evidence. J Am Coll Nutr. 2019 Feb;38(2):97-107. doi: 10.1080/07315724.2018.1497562. Epub 2018 Nov 5. PMID: 30395784.

Kaushik V, Chogale R, Mhaskar S. Alternative Protocol for Hair Damage Assessment and Comparison of Hair Care Treatments. Int J Trichology. 2020 Jan-Feb;12(1):7-15. doi: 10.4103/ijt.ijt_3_20. Epub 2020 Apr 9. PMID: 32549694; PMCID: PMC7276157.

Satchell AC, Saurajen A, Bell C, Barnetson RS. Treatment of dandruff with 5% tea tree oil shampoo. J Am Acad Dermatol. 2002 Dec;47(6):852-5. doi: 10.1067/mjd.2002.122734. PMID: 12451368.

Cooke A, Bedwell C, Campbell M, McGowan L, Ersser SJ, Lavender T. Skin care for healthy babies at term: A systematic review of the evidence. Midwifery. 2018 Jan;56:29-43. doi: 10.1016/j.midw.2017.10.001. Epub 2017 Oct 6. PMID: 29055852.

Maduri VR, Vedachalam A, Kiruthika S. "Castor Oil" - The Culprit of Acute Hair Felting. Int J Trichology. 2017 Jul-Sep;9(3):116-118. doi: 10.4103/ijt.ijt_22_17. PMID: 28932063; PMCID: PMC5596646.

Lee BH, Lee JS, Kim YC. Hair Growth-Promoting Effects of Lavender Oil in C57BL/6 Mice. Toxicol Res. 2016 Apr;32(2):103-8. doi: 10.5487/TR.2016.32.2.103. Epub 2016 Apr 30. PMID: 27123160; PMCID: PMC4843973.

Tirabassi G, Giovannini L, Paggi F, Panin G, Panin F, Papa R, Boscaro M, Balercia G. Possible efficacy of Lavender and Tea tree oils in the treatment of young women affected by mild idiopathic hirsutism. J Endocrinol Invest. 2013 Jan;36(1):50-4. doi: 10.3275/8766. Epub 2012 Nov 26. PMID: 23211454.

Oh JY, Park MA, Kim YC. Peppermint Oil Promotes Hair Growth without Toxic Signs. Toxicol Res. 2014 Dec;30(4):297-304. doi: 10.5487/TR.2014.30.4.297. PMID: 25584150; PMCID: PMC4289931.

Panahi Y, Taghizadeh M, Marzony ET, Sahebkar A. Rosemary oil vs minoxidil 2% for the treatment of androgenetic alopecia: a randomized comparative trial. Skinmed. 2015 Jan-Feb;13(1):15-21. PMID: 25842469.