As mentioned before we are aware that each essential oil is a complex synergy of many different naturally occurring chemical components, each of which brings their own unique property to that particular essential oil. When essential oils are described, they are often described in terms of these properties. However, one does need to keep in mind that, although many essential oils may be described as having the same particular property, they will not all be equal in their effectiveness of that property. We have looked at the essential oil property anti-fungal, so let’s look at the essential oil property – anti-viral.
So what is a Virus?
A virus is microorganism that is smaller than a bacteria. In addition it cannot grow or reproduce outside of a living cell. When a virus invades living cells it uses its own chemical machinery to both keep itself alive, as well as to replicate. Viruses will contain either DNA or RNA as their genetic material. They also have the ability to mutate, and it is this ability that can make treating a specific individual more difficult. Viruses are responsible for causing many common human infections.
Viruses are classified into families and genera depending on:
- the type and size of their nucleic acid
- the type and shape of the capsid
- whether they possess a lipid envelope surrounding the nucleocapsil
According to Professor Brian Tomlinson, a clinical pharmacologist at the Chinese University of Hong Kong (CUHK), it is much easier to produce agents to kill bacteria than ones to kill viruses. This is because of the very nature of the pathogen. Bacteria are living organisms that when multiplying unchecked will damage bodily tissue. However they can be destroyed if their life support systems are cut off. Anti-bacterial agents defeat bacterial infections by attaching enzymes found with the bacteria. This then allows the body’s own immune system to get rid of them. On the other hand, viruses, are parasites which are incapable of reproducing on their own. They remain inactive until such time as they find their way into a host cell. Once there they replicate themselves by taking over the cell’s functions and in the process they destroy the host. Once inside the body they are only vulnerable to anti-viral agents when they have invaded a cell, and there is often the possibility that any treatment may damage the host cell as well as the virus. The ability of a virus to mutate suddenly adds to the challenge in finding an effective agent to eliminate it.
Because of the fact that viruses are parasitic at a cellular level (living and thriving within the cell itself), finding an agent that acts against the virus without damaging the cell becomes more of a challenge. Antiviral activity can be classified as:
- preventing attachment to the host cell
- inhibiting reproduction or growth
Recovery from viral infections requires that the host have an intact immune system. Individuals with compromised or suppressed immune systems often find that their response to antiviral treatment may be delayed and there is the possibility of a reactivation of a latent virus.
Although there is only limited research currently available on the use of essential oils on viruses, the research available does support what we have discovered mainly through traditional use, that some essential oils do have an antiviral effect and that they are able to inhibit the growth of the virus without affecting the host cell.
According to Janetta Bensouilah and Philippa Buck:
Melaleuca alternifolia (tea tree), Mentha piperita(peppermint), Origanum marjorana(marjoram), Eucalyptus globulus (blue gum eucalyptus), Ravensara aromatica(ravintsara), Lavandula latifolia (Spike lavender), Citrus limonum (lemon),Rosmarinus officinalis (rosemary) and Cymbopogon citratus (lemongrass) have been shown to completely inhibit the growth of HSV-1 in vitro at a concentration of 1% [Minami M, Kita M, Nakaya T et al. The inhibitory effect of essential oils on Herpes simplex virus type-1 replication in vitro. Microbiol Immunol. 2003:18:30-5] Lemongrass demonstrated the strongest antiviral activity with complete inhibition at 0.1%. The authors conclude that the antiherpetic activy of the oils is due to direct interaction with the virions by binding to the viral envelopes. The oils were shown to have no direct inhibiting effect on host cell adhesion, penetration or replication and therefore do not offer full cure of HSV-1 infection, but can suppress and prevent infectivity prior to attachment to the host cell.
Janetta Bensouilah and Philippa Buck, Aromadermatology, aromatherapy in the treatment and care of common skin conditions, Radcliff Publishing 2006.
Beverley Hawkins, Aromatherapy 201 Course Notes