Dandruff: what are the effects of nigella seed oil?

The essential point to remember.

Dandruff results from a scalp imbalance, involving both local inflammation and the proliferation of yeasts of the genus Malassezia.
Nigella seed oil exhibits anti-inflammatory properties that are well documented and primarily attributed to its thymoquinone content.
Some antifungal effects have also been observed on Malassezia, but with Nigella oils whose thymoquinone content is higher than what is typically found in the cosmetics market.
No clinical study to date has demonstrated any effect of nigella oil on dandruff.
In cases of dandruff, we recommend turning to active ingredients whose anti-dandruff efficacy has been scientifically proven (ciclopirox olamine, piroctone olamine, ketoconazole...).

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Can black seed oil have an effect on dandruff?

The dandruff corresponds to an excessive shedding of the scalp, visible as white or yellowish flakes, sometimes accompanied by itching or discomfort. It results from an accelerated turnover of scalp keratinocytes, often linked to local inflammation and an imbalance of the skin microbiome. Among the microorganisms involved are yeasts of the genus Malassezia, which are naturally present on the scalp but whose overgrowth disrupts the skin barrier and accelerates keratinocyte renewal.

The active ingredients used to reduce dandruff generally work on two fronts: reducing scalp inflammation and controlling the proliferation of Malassezia.

In this context, the vegetable nigella oil, extracted from black cumin seeds, has attracted interest. Long used in traditional medicine, it is rich in unsaturated fatty acids and bioactive compounds, including thymoquinone. If the nigella oil is primarily recognized for its nourishing properties, it also possesses anti‐inflammatory and antioxidant activities, which could theoretically help soothe an irritated scalp prone to dandruff.

From a mechanistic standpoint, the anti-inflammatory effects of black cumin have been extensively studied, especially with oral intake. A meta-analysis pooling 20 clinical trials with a total of 1,086 participants shows that supplementation withNigella sativa allows to significantly reduce multiple inflammation markers and oxidative stress. A marked decrease in C-reactive protein, TNF-α, and malondialdehyde, a lipid peroxidation marker, was observed, alongside a significant increase in endogenous antioxidant capacities, such as glutathione peroxidase and superoxide dismutase activities. These findings suggest that black cumin modulates specific inflammatory pathways—mechanisms that could be relevant in cases of scalp inflammation due to dandruff, although extrapolation to topical use remains to be discussed.

However, when examining the effect of black cumin oil on Malassezia, the picture is more nuanced. The antifungal properties of black cumin are primarily attributed to the thymoquinone it contains. A study in vitro evaluated various Nigella sativa oils with varying levels of thymoquinone and free fatty acids to observe their antimicrobial activity against several microorganisms, including Malassezia furfur. The results show that the inhibition of Malassezia furfur growth is maximal when the oil contains a high concentration of thymoquinone (around 3%) combined with a low proportion of free fatty acids. Conversely, oils with lower thymoquinone levels display significantly reduced antifungal activity. These data confirm that the observed antifungal effect closely depends on the thymoquinone content of black cumin oil.

Zone d'inhibition de Malassezia furfur pour différentes huiles de nigelle contenant différentes concentrations de thymoquinone (TQ) et d'acides gras libres (FFA). Le pyrithione de zinc est ici utilisé comme contrôle positif. — Inhibition zone of Malassezia furfur for different black seed oils containing varying concentrations of thymoquinone (TQ) and free fatty acids (FFA). Zinc pyrithione is used here as a positive control.
Source: VON OPPEN-BEZALEL L. & al. Antimicrobial activity by a unique composition of cold pressed Nigella sativa seed (black cumin) oil. Food Science and Nutrition Research (2021).

However, in the Nigella seed oils commonly used in cosmetics, thymoquinone is generally present at lower concentrations, most often below 1%. This low level complicates extrapolation of the results obtained in vitro. In other words, although thymoquinone has proven antifungal activity, it is not certain that Nigella seed oil, as it is typically used, contains a sufficient amount to exert a significant effect on Malassezia in the context of dandruff.

To date, no clinical study has evaluated the effect of Nigella sativa oil on dandruff or on scalp flaking associated with the fungus Malassezia.

The available data thus remain indirect and do not allow for a conclusion of genuine anti-dandruff efficacy. Moreover, Nigella sativa oil has a relatively viscous and greasy texture, which can make its application on the scalp impractical, particularly for individuals with fine or oily hair. If necessary, it can be considered as a complementary treatment in very small quantities—for instance, a few drops applied locally to the scalp before shampooing—but it cannot replace a dandruff shampoo or a dandruff treatment formulated with active ingredients whose efficacy has been demonstrated in various clinical studies.