Black seed oil: what are its benefits for the hair?

Even though no clinical study formally demonstrates that applying black seed oil strengthens hair, its composition suggests that it may play a role in protecting and reinforcing hair fibres.

Black cumin seed oil is very rich in unsaturated fatty acids, including oleic acid. The latter is naturally present in the hydrolipidic film that coats the hair fibres, a protective, partly aqueous and partly lipid layer that helps limit their dehydration and reduce the impact of external stressors, such as exposure to UV radiation, wind or temperature fluctuations. By providing lipids similar to those that are physiologically found on the surface of the hair, the application of black cumin oil to the hair may help to strengthen this lipid barrier, although this effect cannot currently be quantified.

Black cumin seed oil also contains a notable proportion of palmitic acid, a saturated fatty acid whose structure resembles that of the lipids found in the cuticle, the outermost layer of the hair shaft. By analogy with other vegetable oils containing saturated fatty acids, it is plausible that these lipids may insert themselves between the cuticle scales and contribute to a better cohesion of the cuticle. A more cohesive cuticle reduces the porosity of the fibre, thereby providing the cortex – the intermediate layer, rich in keratin and essential for hair elasticity – with indirect mechanical protection. This mechanism underpins the idea that the use of black cumin seed oil could be relevant for dry, weakened or damaged hair, even though its efficacy still remains to be demonstrated in clinical studies.

The application of black seed oil to hair fibres could also enhance their appearance and impart shine. As noted above, the saturated fatty acids present in this botanical extract may strengthen the cohesion between the cuticle scales.

When the structure of the hair fibres is strong and the scales that form the cuticle are properly bound together, the hair appears shinier, as it is better able to reflect light.

In the absence of clinical data, this effect of black seed oil remains hypothetical, but it is consistent with current knowledge of cuticle biology. Moreover, applying a vegetable oil such as black seed oil also creates a lipid film on the surface, which provides an immediate glossing effect and helps to visibly enhance the hair’s shine.

Black seed oil may also help to soothe tingling and itching of the scalp thanks to the thymoquinone it contains, a compound with anti-inflammatory properties. This molecule helps to reduce the production of substances responsible for inflammation and to calm excessive skin reactions. Several studies conducted on the skin suggest that black seed oil has genuine soothing potential. In a classical experimental model of skin inflammation, specifically assessing carrageenan-induced oedema, a balm containing 10% black seed oil was able to reduce inflammation to a similar extent as hydrocortisone, a reference anti-inflammatory drug. These findings suggest that its application to the scalp could help to relieve discomfort associated with inflammation.

Even though these data come from an animal model and cannot be directly extrapolated to the human scalp, they reinforce the idea that black seed oil could soothe irritated scalps.

Black seed oil is often cited for its antioxidant potential, largely thanks to thymoquinone. Several studies conducted on the skin have shown that this molecule and, more broadly, black seed oil can stimulate the activity of endogenous antioxidant enzymes, such as superoxide dismutase (SOD), glutathione peroxidase (GPx) and catalase. These enzymes play an important role in neutralising free radicals.

Although no study has directly assessed this effect of black seed oil on hair, it is plausible that its antioxidant potential could contribute, at least in part, to protecting hair fibres from oxidative stress.

The latter is a well‑known factor in the onset of two hair-related issues: premature greying of the hair and the weakening of the ends. On the one hand, free radicals can trigger a series of biochemical reactions that progressively oxidise the melanin present in the cortex, thereby accelerating the appearance of grey hair. In theory, an ingredient rich in antioxidants, such as black seed oil, could help to protect the integrity of melanin for a longer period.

On the other hand, free radicals can alter the lipids and proteins of the hair fibre, particularly keratin, which weakens cuticle cohesion and makes the lengths more vulnerable to breakage and split ends. By strengthening local antioxidant defences, black seed oil could therefore help to limit this progressive degradation.

Black seed oil is often associated with beneficial effects on hair growth and the reduction of hair loss. Its antioxidant properties may help to protect the hair bulb from oxidative stress, a factor involved in the progressive weakening of the follicle and in certain forms of hair loss, thereby contributing to a more favourable environment for hair growth.

Furthermore, the thymoquinone present in black seed oil has anti-inflammatory properties that may influence hair loss. Studies have shown that it may inhibit, in particular, the expression of the COX-2 enzyme and the synthesis of prostaglandin D2 (PGD2), a molecule identified at high concentrations in baldness-affected areas. Its interaction with the GPR44 receptor in the hair follicle appears to promote follicular miniaturisation, that is, the gradual transition from so‑called terminal hairs, which are thick and pigmented, to finer hairs that more closely resemble vellus hair. By reducing the production of PGD2, black seed oil could thus help to limit hair loss.

Several studies support the idea that black cumin seed powder or black cumin seed oil could promote hair growth. One study evaluated the effectiveness of a formulation containing Nigella sativa (10%) incorporated into coconut oil (60%). They tested the formula on groups of rats in which an area of 4 cm² had been shaved. At regular intervals (15, 20, 25 and 30 days), the researchers randomly collected 15 hairs in order to measure their length, while also assessing the total hair weight. The results showed a significant increase in hair growth compared with the control groups.

The authors suggest that this difference might reflect an anticipated transition of follicles from the telogen phase to the anagen phase, possibly stimulated by the antioxidants contained in the plant extracts.

Even though these figures do not allow us to draw conclusions about the effectiveness of black seed oil on its own, they reinforce the idea that some of its components could help to support hair growth.

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

Although further work is still required, particularly with larger samples, this study reinforces the idea that black seed oil could support hair growth.

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