Nigella sativa oil to treat fungal nail infections?

The mycosis of the nail, or onychomycosis, is a fungal infection that most often affects the toenails, but may also involve the fingernails. It is caused by dermatophytes, yeasts or moulds, and presents as nail thickening, discolouration – which can be yellow to brown – and fragility, even the progressive lifting of the nail plate. This infection develops slowly and can be difficult to eradicate due to the dense, keratinised structure of the nail, which constitutes a natural barrier limiting treatment penetration. Although onychomycosis is generally benign, it can become persistent, spread to other nails due to its contagious nature and lead to complications in at-risk populations such as individuals with diabetes or circulatory problems.

In cases of suspected onychomycosis, it is advisable to seek advice from a healthcare professional, such as a pharmacist, who can recommend suitable antifungal treatments to eradicate it.

When faced with this type of nail problem, some people prefer to turn to natural remedies, whether for themselves or for their children. However, the natural origin of a product guarantees neither its efficacy nor its tolerability. Regarding the nigella vegetable oil and nail fungus, its efficacy is far from established. The theoretical interest in nigella often rests on the presence of thymoquinone, a bioactive compound that has demonstrated antibacterial (against both Gram-positive and Gram-negative bacteria) and antifungal properties in various experimental models. However, these effects have mainly been observed with isolated thymoquinone or with concentrated extracts, or even with the nigella essential oil, which contains much higher levels of thymoquinone. Conversely, the nigella vegetable oil contains only a minor proportion, generally below 1%, which makes any significant antifungal activity uncertain when applied topically to the nail.

To date, the only study that might suggest an interest of nigella oil in the context of onychomycosis does not concern its own antifungal activity, but its role as a penetration-enhancing agent for a reference antifungal. The study in question aimed to develop an innovative ketoconazole formulation, a well-known antifungal, in the form of a microemulsion incorporated into a hydrogel, containing nigella oil to enhance penetration. The researchers demonstrated that the formulation combining ketoconazole and nigella oil exhibited improved antifungal activity in vitro against Candida albicans and Aspergillus niger compared with a commercial ketoconazole cream.

In this study, nigella oil was not employed as an antifungal agent but as a vehicle component designed to enhance the product’s diffusion through keratinised structures. Interestingly, the placebo formulation containing nigella oil without ketoconazole also displayed a moderate antifungal activity, suggesting an intrinsic, albeit secondary, biological effect.

However, this study presents major limitations. It does not demonstrate the efficacy of nigella oil alone against nail fungus, but rather its potential as an adjuvant in a complex pharmaceutical formulation. Moreover, the diffusion tests were conducted on porcine skin rather than on actual human nails, which limits the relevance of the results for nail application. Finally, this is a preclinical study, with no clinical evaluation in patients with onychomycosis.

In conclusion, it is currently impossible to assert that Nigella sativa oil can treat onychomycosis of the nail. In cases of onychomycosis, it is preferable to rely on established antifungal treatments recommended by a healthcare professional.

• SPENGLER G. & al. Nigella sativa essential oil and its bioactive compounds as resistance modifiers against Staphylococcus aureus. Phytotherapy Research (2019).

• MOMIN M. & al. Formulation evaluation of ketoconazole microemulsion-loaded hydrogel with nigella oil as a penetration enhancer. Journal of Cosmetic Dermatology (2019).

• WONG A. & al. Onychomycosis: An updated review. Inflammation & Allergy-Drug Targets (2020).

• HAMAAMIN H. H. & al. The antibacterial property of Nigella sativa (black seed) oil against Gram-positive and Gram-negative bacteria. Kurdistan Journal of Applied Research (2021).