Nigella sativa seed oil: what are its benefits for hair?

Although no clinical study has formally demonstrated that applying black cumin oil strengthens hair, its composition suggests that it may play a role in protecting and enhancing the resilience of hair fibres.

Indeed, the black cumin oil is particularly rich in unsaturated fatty acids, including oleic acid. The latter is naturally present in the hydrolipidic film which coats the hair fibres, a protective, semi-aqueous, semi-lipidic mixture that limits dehydration and reduces the impact of external aggressors (UV rays, wind, temperature fluctuations…). By providing lipids similar to those physiologically present on the hair’s surface, applying nigella oil to the hair may help to strengthen this lipid barrier — although this effect cannot be quantified.

It also contains a significant proportion of palmitic acid, a saturated fatty acid whose structure resembles that of the lipids present in the cuticle, the outer layer of the hair. By analogy with other vegetable oils containing saturated fatty acids, it is plausible that these lipids could insert themselves between the scales and contribute to a better cohesion of the cuticle. This could be of interest, as a more coherent cuticle reduces the porosity of the fibre, providing the cortex, the keratin-rich intermediate layer essential to hair elasticity, with indirect mechanical protection. It is this mechanism that leads one to consider the use of black cumin seed oil could be relevant for dry, weakened or damaged hair, even though its efficacy remains to be demonstrated.

The application of nigella seed oil to hair fibres could also confer an attractive appearance and lustre. Indeed, as noted above, the saturated fatty acids present in this botanical extract may bolster the cohesion between the cuticle scales.

When the structure of the hair fibres is strong and the scales forming their cuticle are properly bonded, the hair appears shinier, as it is better able to reflect light.

Let us reiterate that, in the absence of clinical data, this effect of nigella oil remains hypothetical, but it aligns with our understanding of cuticle biology. Moreover, the application of a plant oil such as nigella oil also forms a lipid film on the surface, which provides an immediate glossy effect and helps to visually enhance the hair’s radiance.

Black seed oil could also be an ally against scalp tingling, owing to thymoquinone present in its biochemical composition, its active principle. Indeed, this molecule exhibits anti-inflammatory properties. Studies have notably shown that thymoquinone reduced the production of pro-inflammatory cytokines, such as interleukins 6 and 12 (IL-6 and IL-12) and tumour necrosis factor (TNF-α).

Furthermore, thymoquinone inhibits the nuclear factor NF-κB signalling pathway. NF-κB plays a crucial role in the production of interleukins 1 and 2 (IL-1 and IL-2), other pro-inflammatory cytokines, and interferon-gamma (IFN-γ) in T lymphocytes. IFN-γ is a cytokine produced as part of the innate immune response and involved in regulating various inflammatory mechanisms. Thus, applying black seed oil to the scalp may help to alleviate itching associated with inflammation.

Multiple studies carried out on the skin suggest that nigella oil possesses noteworthy anti-inflammatory potential. One experimental study in particular assessed the anti-inflammatory effect of a 10% nigella oil balm, applied topically to the skin of rats. The researchers employed a standard model of skin inflammation (carrageenan-induced oedema) and observed significant effects, comparable to those achieved with hydrocortisone, a well-documented anti-inflammatory agent.

Although these data originate from an animal model and cannot be directly extrapolated to the human scalp, they reinforce the idea that nigella oil could soothe itching in hair care.

Nigella sativa oil is often cited for its antioxidant potential, largely thanks to thymoquinone, one of its most studied active compounds. Several studies conducted on skin have shown that this molecule and, more broadly, nigella oil, can stimulate the activity of endogenous antioxidant enzymes such as superoxide dismutase (SOD), glutathione peroxidase (GPx) and catalase. These enzymes play a key role in neutralising the free radicals.

Even though no study has directly assessed this effect of nigella oil on hair, it is plausible that its antioxidant potential could contribute, at least in theory, to protecting hair fibres from oxidative stress.

This is a well-known factor in the onset of two hair concerns: premature whitening of hair fibres and the weakening of the ends. Indeed, on the one hand, the oxidative stress is capable of degrade melanin present in the hair cortex. Free radicals can trigger a series of biochemical reactions that progressively oxidise the pigment, thereby accelerating the appearance of grey hair. In theory, an antioxidant-rich ingredient, such as nigella oil, could help to protect the integrity of melanin for longer.

On the other hand, free radicals can also damage lipids and proteins of the hair fibre, particularly keratin, which weakens the cuticle’s cohesion and makes hair lengths more prone to breakage and to split ends. By bolstering local antioxidant defences, nigella oil could therefore help to limit this gradual degradation, although this remains hypothetical in the absence of clinical data.

Many people attribute to nigella oil the ability to stimulate hair growth or to limit hair loss. Indeed, certain biological mechanisms point in this direction. First, its antioxidant properties may contribute to protecting the hair bulb from oxidative stress, a factor often involved in the progressive weakening of the follicle and in certain forms of hair loss. By neutralising free radicals, nigella oil could thus help to maintain an environment more favourable to hair growth.

Moreover, the anti-inflammatory properties of its flagship compound, thymoquinone, may also be pertinent in this context. Studies have demonstrated that it inhibits the expression of the COX-2 enzyme, as well as the synthesis of prostaglandin D2 (PGD2). PGD2, in turn, exerts an inhibitory effect on the hair follicle. Research has indeed revealed the presence of PGD2 at high concentrations in areas affected by alopecia, and its interaction with the GPR44 receptor in the follicle appears to promote its miniaturisation. This contributes to the gradual shift from so-called terminal hairs (thick and pigmented) to finer hairs that more closely resemble vellus. By reducing PGD2 production, black seed oil could therefore protect hair from loss.

Several studies have investigated the effects of black seed oil on hair growth. These studies support the idea that black cumin powder or black seed oil might promote hair development. One study assessed the efficacy of a plant mixture, including Nigella sativa (10%), incorporated into coconut oil (60%). The researchers tested the formulation on two groups of rats from which a 4 cm² area had been shaved. The first group received a daily application of the oil, while the second received no treatment. At regular intervals (15, 20, 25 and 30 days), the researchers randomly sampled 15 hairs to measure their length, also assessing the total hair weight. The results showed a significantly greater growth in the treated animals.

The authors suggest that this difference could reflect an accelerated transition of hair follicles from the telogen to the anagen phase, possibly stimulated by antioxidants present in the plant extracts. Although these results do not permit a definitive conclusion regarding the efficacy of nigella oil alone, they reinforce the idea that certain of its constituents could, in theory, contribute to supporting hair growth.

These results are supported by a clinical study involving 20 patients with telogen effluvium, a form of diffuse hair loss associated with a premature shift of follicles into the telogen phase. For three months, half of the participants applied daily a lotion containing 0.5% oil of Nigella sativa, while the others received an identical formulation but without nigella extract. The results show a significant increase in hair density and thickness among the patients who received nigella.

Although further research is still necessary, particularly with a larger sample size, this study reinforces the idea that nigella oil could support hair growth.

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