Nigella sativa oil: effective against cold sores?

Oral herpes: can Nigella sativa oil halt a cold sore outbreak?

Lip herpes, also known as cold sores or fever blisters, is a common viral infection caused by herpes simplex virus type 1 (HSV-1). Among the traditional remedies often recommended is nigella seed oil. But what is the actual efficacy of this plant-derived oil against cold sores? Does it do more good than harm? Let us answer these questions together.

Published on February 2, 2026, updated on February 2, 2026, by Pauline, Chemical Engineer — 7 min of reading

Key points to remember.

Herpes labialis is a contagious viral infection linked to the HSV-1 virus, which is often reactivated by stress, fatigue or a weakened immune system.
Nigella sativa oil possesses anti-inflammatory and immunomodulatory properties which can theoretically help modulate the inflammatory response associated with a cold sore.
Some studies in vitro suggest an antiviral activity of compounds from the genus Nigella, but this does not apply to Nigella sativa, from which the oil used in phytotherapy is extracted.
To date, no clinical study has demonstrated the efficacy of nigella oil against labial herpes.
Nigella oil should never be applied undiluted, all the more so on a cold sore.
In the case of a cold sore, antiviral treatments with proven efficacy remain the standard of care.

Nigella sativa oil and cold sores: how does it work?

Cold sores are a common viral infection caused by herpes simplex virus type 1 (HSV-1). Following a primary infection, which often occurs in childhood, the virus remains latent in the body and can reactivate intermittently, particularly during periods of fatigue, stress or reduced immune defences. These reactivations present as tingling or burning sensations, followed by the emergence of painful vesicles clustered around the lips. Although benign in immunocompetent individuals, labial herpes is contagious, recurrent and can cause aesthetic and functional discomfort, hence the importance of addressing it at the first sign of symptoms.

Although it may be tempting, it is important not to manipulate a cold sore. Should this happen, wash your hands immediately and refrain from touching your eyes to prevent keratitis.

Theoretically, the nigella oil could be of interest against labial herpes due to its immunomodulatory properties. Several studies suggest that the oil extracted from Nigella sativa is capable of influencing certain immune responses, notably by modulating the balance between Th1- and Th2-type inflammatory responses. Furthermore, several investigations indicate that nigella oil can act on key cells of adaptive immunity, notably T lymphocytes. Studies carried out in animals and humans have highlighted an increase in regulatory lymphocytes (CD4+CD25+) and a modulation of the CD4/CD8 ratio after supplementation with nigella oil, associated with a reduction in systemic inflammatory markers such as CRP.

However, HSV-1 reactivation is favoured by periods of immune stress or local inflammation. By contributing to the reduction of certain pro-inflammatory mediators, such as IL-4, IL-5 and IL-6, as demonstrated in various animal models, and by promoting a more balanced immune response, Nigella sativa oil could help to prevent outbreaks that lead to cold sores.

Furthermore, an experimental study focused on the antiviral activity of compounds isolated from the seeds of Nigella damascena against herpes simplex virus type 1. The researchers extracted and characterised several dolabellane-type diterpenes, then evaluated their capacity to inhibit viral replication in vitrousing a plaque-reduction assay on Vero cells. Several of these compounds demonstrated a significant inhibition of HSV-1, with effects noted at low concentrations. Some of the diterpenes exhibited activity comparable to, or slightly exceeding, that of oleanolic acid—a natural reference compound known for its anti-HSV-1 properties—although their efficacy remains lower than that of acyclovir, the benchmark antiviral treatment.

Compound	Concentration (µM)	Inhibition (%)
Diterpene from Nigella damascena (1)	10	24.1
Diterpene from Nigella damascena (1)	2.5	19.0
Diterpene from Nigella damascena (1)	1	9.3
Diterpene from Nigella damascena (2)	10	32.0
Diterpene from Nigella damascena (2)	2.5	19.9
Diterpene from Nigella damascena (2)	1	0.0
Oleanolic acid	10	42.1
Oleanolic acid	2.5	13.1
Oleanolic acid	1	0.3
Aciclovir	10	86.7
Aciclovir	2.5	57.5
Aciclovir	1	32.5

Inhibitory effects of compounds isolated from Nigella damascena against HSV-A in Vero cells.

Source: OGAWA K. & al. New diterpenes from Nigella damascena seeds and their antiviral activities against herpes simplex virus type-1. Journal of Natural Medicines (2018).

However, these results must be interpreted with caution.

On the one hand, this concerns data in vitro obtained from purified molecules and not from a vegetable oil applied to the skin. On the other hand, the species studied is not Nigella sativa, the one commonly used in cosmetics and herbal medicine, but Nigella damascena, a plant primarily grown for its ornamental value, whose chemical composition differs significantly. The active diterpenes identified are not known to be present in nigella oil derived from Nigella sativa. Thus, although this study confirms that certain molecules from the genus Nigella can interact with HSV-1, it does not allow conclusions to be drawn regarding the efficacy of the oil extracted from Nigella sativa against cold sores.

If you are nevertheless considering using nigella oil in case of a cold sore, be aware that this oil should never be applied undiluted, as it has been linked to several adverse reactions when used without dilution. If you experience symptoms suggestive of labial herpes, we recommend that you seek advice from a pharmacist or healthcare professional.