Hair oils: Science behind its use in hair care

Hair oil application has been the basic hair care remedy for beautiful, black, luscious hair especially in Indian females (and for some males who groom their beard religiously :P). We’ve been taught at a very early age about hair grooming, mothers would be seen applying and massaging layers of oil into their daughters scalp while enjoying the afternoon sun.

I remember during my time living in Kerala (southern tropical state in India, where the inhabitants use coconut il for everything, from cooking to hair grooming). Girls there has long thick hair touching their knees, but it was always covered in coconut oil so I could never appreciate the overall health status of their hair. I couldn’t tell if the shine was natural or because of the layer of oil, the split ends were beautifully hidden as well. But this was the norm there, they love having oil on their hair day and night and it seems to work for them.

Personally for me, as someone with fine hair, which can get oily pretty quick even just after a day post hair wash, hair oiling never played an important part in my hair grooming process.

Individuals with thin fine hair do experience oiliness of the hair quicker than those with thicker hair, as the sebum produced in our scalp can be transmitted to the hair shaft easily.

As a dermatologist, I often get question on which oil is best to use, how frequently is it to be used, is pre or post shower hair oiling better and so on and so forth.

Honestly, there is no right answer to these questions, as there are very few scientific studies done to compare between the various hair oils or their methods of application.

Lets see which hair oil actually have science backing up its claim

Coconut oil

Studies have found that coconut oil is able to penetrate the hair shaft and this can be enhanced by application of warm oil. The oil coats the hair, prevents absorption of moisture into the hair and thus prevent the recurrent swelling and shrinking up of hair cortex which is responsible for hair fragility and breakage.

Coconut oil has been found to be the only oil to prevent protein loss from the hair shaft, thus providing more stability to the hair.

Photo credit: Photo by Marvin Meyer on Unsplash

Sunflower oil

Though this oil also provides hydration to the hair similar to coconut oil by forming a film coat on the hair . It however cannot prevent protein loss from the hair shaft due to its bulky nature and presence of double bonds that prevent penetration into the hair fibre.

Articles that claims its beneficial effect on hair are based on the study of the effect of Vitamin E on hair growth. A study of 39 patients (note- small sample size) showed that oral vitamin E supplementation for a period of 8 months had positive outcome on patients suffering from hair loss. Sunflower oil is also rich in Vitamin E, but it doesn’t necessarily mean that topical application of a vitamin E rich oil will also achieve the same result as daily oral supplementation.

Moroccon argan oil

Another oil rich in vitamin E, the argan tree is endemic to Morocco, has emerged as the most expensive essential oil and as a popular hair cosmetic from shampoos, to conditioners to hair oils.

Is it worth the hype?

There are no scientific evidence for its use in hair care so far, the only reason for its popularity is that its rich in Vitamin E (a potent anti-oxidant) and the study mentioned above, of Vitamin E positive effect on hair growth.

Almond oil

Again rich in Vitamin E, though it has lots of health benefits when consumed. The effects of almond oil in hair, except for its emollient action i.e coats an oily film on the hair and prevents breakage, no other scientific data available for stimulating hair growth.

Olive oil

Compound found in olive oil such as oleuropein (promotes anagen hair growth -active growing phase of hair, in mouse skin. No human studies yet.

Oleocanthal an anti-inflammatory phenolic compound found in olive oil, when consumed orally is known to help reduce inflammation. Again no data on its effect when applied topically.

image credit:Photo by Roberta Sorge on Unsplash

Rosemary oil

Unlike other oils which lacks strong scientific evidence backing up their claims in promoting hair growth, rosemary oil actually helps improve microcirculation ( improves blood flow to skin). It has been compared to be equally effective to 2% minoxidil in the treatment of androgenetic alopecia (male pattern hair loss). Increase in hair count were seen only after 6 months of daily application.

Whether minoxidil can be completely replaced by rosemary oil, the answer is still “NO”. Because though it was seen to be as effective as 2% minoxidil, we normally prescribe a 5%-10% strength of minoxidil in dermatology.

Hibiscus oil

An animal study concluded that extracts from the leaves of hibiscus plant does promote terminal hair growth. No new hair follicles were formed.

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Onion Juice extract

Crude onion juice extract was used in a study of patients with alopecia areata (auto-immune condition causing patchy hair loss) which is different from diffuse hair loss from other causes. Daily topical application of onion juice to the area of hair loss showed significant improvement in the form of new terminal hair (dark, thick hair) at the end of 6 weeks.

How it works is thought to be by “antigenic competition” ( my fellow dermatologist will understand this term.:P

To summarise

Hair oils (all types; from coconut, almond, olive, vegetable oil etc) are beneficial in a way that they form an oily film on the hair shaft and prevents excess moisture absorption from the environment and prevents water loss from the hair cortex. This is important because the recurrent swelling (from absorbing water) & shrinking (from losing water) of the hair cortex is responsible for the fragility, split ends and eventually breaking off of the hair from its weakest point (which can be seen as hair fall).

Oiling hair can prevent split ends, strengthen the hair (coconut oil) and reduces the friction that arises when combing the hair. Thus, helps manage frizzy hair, gives the hair shine and tames the fly aways.

With regards to stimulating hair growth, only rosemary oil has scientific data backing up its claim.

Olive oil could have potential based on the studies available. Still no conclusive data yet as a topical application.

Heat i.e warm oil application helps the oil to penetrate into the hair fibre and leaving just a thin film on the hair shaft, giving a less oily appearance.

Regarding how to use hair oils, frequency, duration, sadly I do not have the right foolproof answer for this. My personal advice based on my understanding of the research on this topic is :

Coconut oil is definitely the hero here, its the best, safest & cheapest option, especially if you have dry, frizzy, splits ends, apply it on you hair from root to tip. It has the additional advantage of preventing protein loss from the hair. There is actually no need to apply to the scalp, as your skin produces sebum naturally. But go ahead if you have dry scalp or if you enjoy the head massages.

Since we all do not like walking around with oily hair, and since we have products like conditioners & hair serums to use post showers, to make our hair more soft, shiny and manageable, reserve hair oil application for pre-showers. Applying too much & leaving the hair oil for too long will only attract more dirt to your hair which will make it difficult washing the oil out from the hair. Extra manual effort of massaging the shampoo will only cause more friction which can lead to increase falling of hair in the shower.

You can use hair oils as frequent as you like, all the studies reporting positive effects is based on daily hair oil application. I know its impossible to keep up with this in real life, so be flexible, go with your flow. ( I know, not a very scientific advise, but there is no clear cut science behind it yet!! )

Do not depend on hair oils to fix all your hair issues. It should only be a complimentary step to your already existing hair care (shampooing, conditioning, serums, or hair treatment such as minoxidil).

And lastly, if you have straight, non frizzy hair and you’re not in the habit to apply hair oil, then thats also okay. You do not need to follow the crowd.