Hair Oils: Indigenous Knowledge Revisited.

Hair oils are used all over the world since time immemorial; however, their exact effect on the hair and scalp remains obscure. They are usually easily accessible and are inexpensive. A wide variety of oils have been used and newer ones are coming up every day. The primary function of most of the hair oils is to act like an emollient but the unique characteristics of various hair oils suggests its action just more than emollient action. This article focuses on the different types of hair oils and their possible beneficial effects on the hair. Dermatologists need to be aware of the effects of hair oils and their usage. Copyright:

INTRODUCTION

In India and different parts of the world, oils have been used on the scalp with the belief that, hair oils in the long run prevents hair loss, brings shine, volume to the hair and prevents graying of hair. Hair oiling involves combing the hair, which is followed by oiling from the roots to the tips of the hair often with a hair braid once a week before shampooing. This belief has been exploited by the cosmeceutical industry, with numerous personal hair care products available over the counter. Dermatologists are frequently consulted for advice on hair oils and hence the need to know about the common hair oils.

This article will discuss the various types of hair oils used in India, their chemical composition, possible effects, and uses.

METHODS OF SEARCH

For this review a systemic literature search in ScienceDirect, ReasearchGate, PubMed, Google Scholar, Wiley Online Library, SpringerLink, and free E articles. The search keywords were hair oils, fungal and oils, amla oil and hair, coconut oil and hair, argon oil, linseed oil, fenugreek, fenugreek and hair, fenugreek and alopecia, fenugreek and fungus.

TYPES OF HAIR OILS

As per the “Indian Cosmetic Market Outlook 2018 (https://www.prnewswire.com/news-releases/indian-cosmetic-market-outlook-2018-300054773.html) accessed on date December 21, 2020), the share of hair- care products is huge in the cosmetic industry, with hair oils dominating the market.

A survey done on Indian hair oils in karnal city showed olive oil (® keo karpin, ® Brahmi Amla), coconut oil, almond hair oil, argan hair oil (® Vatika hair oil) where among the top preferences by Indian people. The article reviews hair oils commonly used in India which are listed in Text Box 1.

Text Box 1

List of hair oils discussed in this article

Coconut oil

Almond oil

Castor oil

Argan oil

Olive oil

Amla oil

Fenugreek oil

Sesame oil

Linseed oil

Mustard oil

It is clarified here that scientific material available on these topics is limited, and exaggerated claims are made about their effects, without adequate substantiation or evidence-based data in peer-reviewed journals. An attempt is made to revelant summarize material for which substantion was available.

Coconut oil

It is obtained from the fruits of Cocus nucifera widely used in south India particularly along the coasts. It is highly popular in India, Sri Lanka, Indonesia, Malaysia, Australia, and South America.

Chemical composition

It consists of saturated fatty acids and is one of the richest sources of medium chain fatty acids. The major fatty acids present are myristic acid, capric acid, lauric acid,[1] and monolaurin. It also contains phenolic acids and antioxidants such as tocopherol.[2]

Effects on hair: Coconut oil has been claimed to have various actions on the scalp, on the hair such as:

Saponification – Coconut oil is a good saponification agent and so has been used in shampoos[3]

Antibacterial activity – Monolaurin has shown its efficacy as an antibacterial agent. It acts by disintegrating the lipid membrane of different bacteria such as Propionibacterium acne, Staphylococcus aureus, Staphylococcus epidermidis.[4] Coconut oil in concentrations of 5% to 40% (w/w) exhibited bactericidal activity against Pseudomonas aeruginosa, Escherichia coli, Proteus vulgaris, and Bacillus subtilis[5]

Antifungal activity – Monolaurin exhibits antifungal activity[6]

Emollients – Coconut oil forms a coating over the hair shaft, thereby sealing the cuticle and traps the moisture inside[7]

Lubricant – It provides increased slip in between the hair strands, so detangles the hair, smoothens and flattens the cuticle surface which improves the health and appearance of the strands[8]

Preventing protein loss – Due to its low molecular weight and straight linear chain it is able to penetrate inside the hair shaft thereby, preventing loss of protein from the hair.[9]

Coconut oil therefore found wide acceptability for use in several parts of the world.

Almond oil

The oil is obtained from fruits of Prunus amygdalus which is native to Middle East and South America. In Ayurveda this oil has been known to have aphrodisiac property.[10]

It consists of monosaturated fatty acid, polyunsaturated fatty acid (linoleic acid) and Oleic acid. It also consists of linolenic acid, stearic acid, palmitic acid. It is also a rich source of vitamin E.[11]

Effects on hair:

Protection against ultraviolet (UV) damage – Almond oil has fatty acids that are rich in double bonds and hence has shown to protect against UV radiation induced structural damage[12]

Emollient – It has emollient property, and hence can be used to soften and moisturize dry hair[13]

Elasticity – It has been reported to increase the elasticity of the hair as it fills the gap between cuticle cells[7]

Protein loss – The oil has no favorable impact on protein loss as it is not able to penetrate inside the hair shaft.[9]

Castor oil

The oil is from the seeds of a Ricinus communis that is found in all tropical and sub-tropical countries and is the major producer among all. The oil is filtered and steamed to remove ricin a toxic component in the oil that causes rancidity of the oil.[11]

It consists glycerides of isoricinoleic acid, ricinoleic, dihydroxy-stearic acid, stearic acid,[11] eicosanoic acid, linolenic acid, palmitic, and linolenic acid.

Effects on hair: Castor oil is popular as hair oil, with the following actions:

Moisturizing effect – Ricinoleic acid and its derivatives present in the oil have moisturizing quality[14]

Nourishing effect – The fatty acids have very good penetrability and have been claimed to provide nourishment to the hair follicle[15]

Germicidal and fungicidal effect – Ricin and ricinoleic acid present in the oil protects the scalp and the shaft of the hair from fungal and microbial infections[15]

In androgenetic alopecia – Ricinoleic acid has been shown to penetrate skin and act as an inhibitor of prostaglandin D2 synthase (PGD2). Ricinoleic acid has a two-dimensional structure, which is very similar to the prostaglandin family and has also been demonstrated to have some degree of effect on hair growth.[16]

Argan oil

The oil is obtained from the kernels of Argania spinose found in the desert regions of Morocco. The kernels are roasted, cooled and grinded to get the oil. The oil is allowed to stand and then decanted, filtered to remove any impurities. Conventionally, it has been used in cooking, in the treatment of skin infections and in skin and hair products.[13] In the last 15 years, Argan oil has emerged as an important ingredient of many cosmeceutical products.[7]

It is composed of monosaturated (80%), saturated (20%) fatty acids.[13] It contains sterols, polyphenols, tocopherols, triterpene alcohols, squalene, palmitic, stearic, linolenic, and linoleic acid.[17]

Effects on hair: Effects of Argan oil are:

Sebostatic – The high oleic acid content has been found to have regulatory effect on sebum secretion[7]

Moisturizing effect – The oil is considered to have a very good water holding capacity[13]

Increase in elasticity – Topical application of Argan oil has shown statistically significant increase in gross elasticity, net elasticity, and biological elasticity at 2 months compared to baseline.[18]

Olive oil

It is extracted from the pericarp of fruits of Olea europoea from the plants native to Mediterranean countries. The seeds of the fruit are pressed lightly to extract the oil. This oil is mixed with water to remove any impurities. Unsurprisingly, olive oil has been used in hair cosmetics and as a skin product since a long time in several cultures.[13]

The oil contains arachin, linolein, and palmitin. However, the main component is olein.[19] It also contains sterols, carotenoids, triterpenic oils, and phenolic compounds. The virgin olive oil is a rich source of antioxidants that contains flavonoids, lignans, and secoiridoids.[20]

Effects on hair:

Emollient effect – Olive oil has an emollient function by sealing the cuticle and trapping the moisture inside; however, coconut oil remains superior in this regard[7]

Photo protection – Olive oil is protective against UVB due to the presence of extra virgin olive oil. Hydroxytyrosol, one of the key polyphenolic components of olive oil, has been studied recently for its effects on UV-A induced cell damage and has shown to combat reactive oxygen species (ROS) induced by UV light[21]

Antifungal effect – Olive oil has a definite inhibitory influence on the ability of the fungus Microsporum gypseum and Trichophyton vanbreuseghemii to penetrate the hair. The effect may be specific or purely a result of “mechanical barrier.”[22] A recent study showed the antifungal activity of the aliphatic aldehydes in olives-hexanal, nonanal, (E)-2-hexenal, (E)-2-heptenal, (E)-2-octenal and (E)-2-nonenal-against six strains of Trichophyton mentagrophytes, one strain of Microsporum canis and seven strains of Candida spp[21]

In psoriasis – Olive oil has shown promising results when used in combination with different ingredients. A mixture of honey, olive oil, and beeswax mixture (1:1:1) has demonstrated significant improvement in the symptoms such as redness, scaling, thickening, and pruritis. This is due to its antioxidant action and hydroxytyrosol-induced apoptosis and inhibition of cell proliferation.[21]

Amla oil

It is also known as the Indian gooseberry. It is obtained from deciduous tree Emblica officinalis widely found in India. It is grown in Gujarat, Uttar Pradesh, Maharashtra, and Rajasthan.[23] It is the richest source of Vitamin C.

Effects on hair:

Antifungal effect – Amla oil is fungicidal to M. canis, M. gypseum, Trichophyton rubrum at 0.5% concentration. The effect is due to the presence of unsaturated C18 fatty acids[25]

Graying of hair – Graying of hair is thought to be mediated through ROS leading to damage of the melanocytes, thereby leading to decreased pigmentation.[26] Amla oil, because of the presence of Vitamin C, gallic acid, ellagic acid, and tannins can absorb ROS[27]

Anti-microbial – Amla oil has shown potent antibacterial activity against E. coli, Klebsiella pneumonia, Klebsiella ozaenae, Proteus mirabalis, P. aeruginosa, and Salmonella typhi.[27]

Fenugreek oil

Fenugreek (Trigonella foenum graecum L) is also known as Greek hay and is known as Bockshornklee in Germany.[28] In India, fenugreek is grown as a cover crop as the plant grows quickly. It is a leguminous herb about 2 feet height.[23] The major producers are Rajasthan, Gujarat, Uttar Pradesh, and Tamil Nadu.

Diosgenin is a steroid sapogenin which is found in fenugreek. Other sapogenins found in yamogenin, gitogenin, tigogenin, and neotigogens. It also contains alkaloids such as trigonelline, gentianine, and carpine compounds.[29]

Effects on hair:

Androgenetic alopecia – Fenugreek seeds have received wide publicity in social media as an antiandrogen of plant origin. While the possible mechanism of action is not properly known, diosgenin in fenugreek has been shown to have oestrogenic activity which may lead to inhibition of dihydrotestosterone.[3031] Flavonoids and Trigonelline cause vasodilation in the scalp.[32] Flavonoids have also been shown to have anti-inflammatory and anti-proliferative effect[31]

Anti-fungal effect – It has fungicidal effect against Trichoderma viride, Aspergillus niger, Aspergillus oryzae and Aspergillus flavus. It also has effect against harmful pathogenic fungi - Fusarium graminearum[33]

Bactericidal activity – The seed extracts are effective against E. coli, S. typhi and S. aureus

Pityriasis sicca – A study done by Verma et al., demonstrated that the 1 ml of fenugreek extract with 3 ml of water (1:4) was found to be effective in declining the Malassezia furfur[34]

Emollient – Fenugreek has lecithin which is a natural emollient and helps in strengthening and moisturization of hair.[35]

Sesame oil

It is also known as til oil in India. It is indigenous to India, commercially produced in Gujarat, Orissa, Madhya Pradesh, Andhra Pradesh, Uttar Pradesh, Rajasthan, Punjab, Karnataka.[23] It is also found in Egypt, Middle East, and China. The seeds of Sesamum indicum are pressed to obtain oil.[11]

Sesame oil contains Palmitic acid, oleic acid, linoleic acid, linolenic acid, gandoleic acid, behenic acid, stearic acid, and arachidic acid. It contains high amounts of sesamolin, sesaminol, sesamin.[13] Sesamol provides stability to the oil.[11] It also contains sesame lignans.[36]

Effects on hair:

Anti-inflammatory properties – The lignans present in sesame oil have anti-inflammatory properties[36]

Antioxidant effect – Sesame oil is resistant to oxidative deterioration because of the presence of endogenous antioxidants such as sesamolinol, sesaminol. A significant in vivo, antioxidant activity of sesamolin came from its metabolites, sesamolinol and sesamol, when sesamolin was supplemented in rats' diet[37]

UV-induced damage – It has been seen in a study done on rats that tocopherol + tocotrienol + sesamin extract significantly reduced the UV-induced damage.[37] It forms a protective coat around the hair, there by preventing hair damage[38]

Anti-bacterial effect – Sesamin has been found to have remarkable antibacterial activity against E. coli, S. aureus, P. aeruginosa, Shigella flexneri. The minimum inhibition concentration for all these organisms were <0.1%. The antibacterial activity of Sesamin is mainly due to bactericidal effect rather than bacteriostatic effect[37]

Moisturizing agent – It moisturizes the hair follicle and prevents dryness. It has enhanced penetration capacity[38]

Hair growth – As the oil has enhanced penetration and reaches up to the hair follicle, it increases the circulation of the scalp, thereby increasing hair growth and reduce graying of hair.[38]

Mustard oil

Mustard oil, from the seeds of plant Brassica nigra is cultivated in India, China, Canada, and England and is known as sarson ka tel.[11]

It consists of arachidic, behenic, linoleic, linolenic, oleic, palmitic, erucic, lignoceric, and myristic acid.[39] It also consists of carotenoids, tocopherol, and sinigrin.[40]

Effects on hair:

Anti-oxidant property – It contains amino acids, cysteine which acts as antioxidant. Cystiene protects the body from free radicals which damage DNA and cell membranes[41]

Acts a sunscreen – Due to its thick consistency and high vitamin E, topical application of oil protects against harsh UV rays[41]

Antifungal: Mustard oil significantly inhibits the penetration of T. mentagrophytes in the hair[42] but is less effective in comparison coconut and amla oil against the fungus[25]

Antimicrobial – It has a broad-spectrum antimicrobial activity and has shown activity against S. aureus, E. coli, and C. albicans. The action may be due to the presence of phenol, flavonoids, alkaloids, sterols, and terpenes which may be responsible for antimicrobial activity.

Thus, it can be seen that these oils have been attributed to have different properties which are summarized in Table 1.

Table 1

Summary of oils, chemical composition and its effect on hair

Oils	Chemical composition	Effects on hair
Coconut	Myristic acid, capric acid, lauric acid, monolaurin, phenolic acids and tocopherol	Saponification agent Antibacterial - Due to monolaurin Antifungal- Due to monolaurin Emollient action - Due to formation of coating over the hair shaft Lubricant - Smoothens and flattens the cuticle surface Prevents protein loss
Almond	Monosaturated fatty acid, polyunsaturated fatty acid (linoleic acid) and oleic acid, linolenic acid, stearic acid, palmitic acid, Vitamin E	Protection against UV damage - Due to its property to have multiple double bonds which interfere with the light-induced degradation Emollient Elasticity - Fills the gap between the cuticles
Castor	Glycerides of isoricinoleic acid, ricinoleic, dihydroxy-stearic acid, stearic acid, eicosanoic acid, linolenic acid, palmitic and linolenic acid	Moisturizing effect - Ricinoleic acid has been attributed that quality Nourishing effect - Due to good penetration capacity Germicidal and fungicidal - Ricin, ricinoleic acid has antifungal properties Androgenetic alopecia - Ricinoleic acid is a potential inhibitor of PGD2
Argon	Monosaturated (80%), saturated (20%) fatty acids, sterols, polyphenols, tocopherols, triterpene alcohols, squalene, palmitic, stearic, linolenic and linoleic acid	Sebosatic - Oleic acid has regulatory effect on sebum Moisturizer - Due to good water holding capacity Increase in elasticity - Overall elasticity of the hair is increased
Olive	Arachin, linolein, palmitin, olein, sterols, carotenoids, triterpenic oils and phenolic compounds, flavonoids, lignans and secoiridoids	Emollient - Seals of the cuticle Photoprotection - Hydroxytyrosol provides protection against UVB as its combats ROS Antifungal effect - Inhibitory effect against fungus due to mechanical barrier and also because of the presence of the aliphatic aldehydes in olives- hexanal, nonanal, (E)-2-hexenal, (E)-2-heptenal, (E)-2-octenal and (E)-2-nonenal Psoriasis - hydroxytyrosol as anti-oxidant property, inhibit cell proliferation and induce apoptosis
Amla	Emblicanin A and B, punigluconin, pedunculagin, chebulinic acid (ellagitannin), chebulagic acid (benzopyran tannin), corilagin (ellagitannin), geraniin (dehydroellagitannin), ellagotannin phyllantine, phyllembein, phyllantidine, gallic acid, methyl gallate, ellagic acid, trigallayl glucose glutamic acid, proline, aspartic acid, alanine, cystine, lysine, pectin, ascorbic acid, quercetin, kaempferol, citric acid	Antifungal - Presence of unsaturated C18 fatty acid, shows inhibition against Microsporum canis, Microsporum gypseum, Trichophyton rubrum Graying of hair - Due to presence of Vitamin C, together with gallic acid, ellagic acid and tannins Anti-microbial - Potent antibacterial activity against Escherichia coli, Klebsiella pneumonia, Klebsiella ozaenae, Proteus mirabalis, Pseudomonas aeruginosa, Salmonella typhi
Fenugreek	Diosgenin, yamogenin, gitogenin, tigogenin and neotigogens, trigonelline, gentianine, and carpine compounds	Androgenetic alopecia - Diosgenin, has oestrogenic activity. Therefore, more testosterone is metabolized to oestradiol, reducing the formation of DHT which damages the hair root. Flavonoids are important for increasing blood cells and help in increasing the blood circulate in scalp. Trigonelline causes blood vessels dilation in the scalp Anti-fungal effect - Inhibition of growth against Trichoderma viride, Aspergillus niger, Aspergillus oryzae and Aspergillus flavus Bacterial activity - Seed extracts are effective against Escherichia coli, Salmonella typhi and Staphylococcus aureus Pityriasis sicca - Fenugreek extract was functional in inhibiting the growth of malassezia furfur Emollient - Lecithin which is a natural emollient and helps in strengthening and moisturization of hair
Sesame	Palmitic acid, oleic acid, linoleic acid, linolenic acid, gandoleic acid, behenic acid, stearic acid and arachidic acid, sesamolin, sesaminol, sesamin, sesame lignans	Anti-inflammatory - Lignans present in sesame oil has anti-inflammatory properties Anti-oxidant - Sesame oil is resistant to oxidative deterioration because of the presence of endogenous antioxidants such as sesamolinol, sesaminol UV induced damage - It forms a protective coat thereby preventing damage Anti-bacterial - Sesamin has been found to have remarkable antibacterial activity. Antibacterial activity mainly due to bactericidal effect Moisturizer - Due to enhanced penetration capacity it moisturizes the hair follicles Hair growth - Oil has enhanced penetration and reaches upto the hair follicle, it increases the circulation of the scalp thereby increasing hair growth
Mustard	Arachidic, behenic, linoleic, linolenic, oleic, palmitic, erucic, lignoceric and myristic acid, carotenoids, tocopherol and sinigrin	Anti-oxidant - It contains amino acids, cysteine which acts as antioxidant. Cystiene protects the body from free radicals which damage DNA and cell membranes Sunscreen - Its thick consistency and high Vitamin E, topical application of oil protects against the harsh UV rays Anti-fungal - Mustard oil significantly inhibits the penetration of Trichophyton mentagrophytes in the hair Anti-microbial - Broad-spectrum antimicrobial activity, due to the presence of phenol, flavonoids, alkaloids, sterols, terpenes which may be responsible for antimicrobial activity

UV – Ultraviolet; ROS – Reactive oxygen species; UVB – Ultraviolet B; DHT – Dihydrotestosterone

SUMMARY

The cosmetic market for hair oils is huge and is growing exponentially. Scientific proof for the claimed effects is being discovered in recent studies, but further studies are needed to precisely define the mechanism of action. However, because of their popularity, which is further exaggerated by social media discussions, it is important that dermatologists are aware of their possible effects and role in trichology.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

Text Box 2

Chemical composition of amla oil

Hydrolysable tannins - Emblicanin A and B, punigluconin, pedunculagin, chebulinic acid (ellagitannin), chebulagic acid (benzopyran tannin), corilagin (ellagitannin), geraniin (dehydroellagitannin), ellagotannin

Alkaloids present are - Phyllantine, phyllembein, phyllantidine

Phenolic compounds - Gallic acid, methyl gallate, ellagic acid, trigallayl glucose

Amino acids - Glutamic acid, proline, aspartic acid, alanine, cystine, lysine

Carbohydrates - Pectin

Vitamins - Ascorbic acid

Flavinoids - Quercetin, kaempferol

Organic acids - Citric acid[24]