'Anti-viral essential oils' is a popular subject on the web. Here's a quick look at the most highly recommended antiviral essential oils used in aroma-medicine:

Hyssop - Hyssop essential oil is unique in its chemical makeup, a feature which gives it a very broad range of effects. Hyssop contains 7 of the 9 major chemical classes found in essential oils. The Hyssop officinalis decumbens variety is considered safe but very effective (other Hyssop chemotypes are high in certain ketones which should generally be avoided). Its camphorus, herbaceous aroma is somewhat medicinal, but not unpleasant. An excellent choice for diffuser use, or diluted and massaged into lymph nodes or above and below the balls of the feet.

Ravensara - similar to Eucalyptus with a high Cineol content (indicated for respiratory conditions) though much more chemically complex. Battagila says in the Complete Book of Aromatherapy: "Its tolerability and strong antiviral action make it the oil of choice for the treatment of influenza."

Melissa - this herb has a wide variety of effects. It yields a small amount of precious essential oil, one of aromatherapy's favorites. The essential oil has been studied significantly for treatment of HSV-1 and 2, with statements being made by German researchers that use of the oil can cause complete remission of Herpes Simplex. It seems to have a wonderful effect on the immune system, contributing not only by actually eradicating certain viruses, but in a more holistic way as well. Only very low concentrations of the oil are necessary for use - some say dilutions as low as 1:100 will be completely effective.

Thyme c.t. Linalool - Thyme has long been used to treat infectious illness, and is indicated for treatment of Influenza, and flu-like symptoms. Thyme c.t. linalool contains Thymol and Carvacrol - the same constituents found in the heavy-hitter Oregano oil, with of course 'linalool', the sweeter component of the oil. Linalool itself has been shown to have anti-viral action.

Sweet Basil - The oil from Ocimum basilicum herb has been used medicinally for centuries. Several of the compounds in Basil have been positively studied for anti-viral activity, including ursolic acid. apigenin and linalool. Sweet Basil is a wonderful aromatic, and is listed on the GRAS (generally recognized as safe) list from the FDA as being safe to ingest in small amounts. We would consider this to be one or two drops at a time, a few times per day.

Bay Laurel - Bay Laurel, also known as Laurel Leaf or Laurus Nobilis was the subject of an Italian study in 2008 which noted 'intesting activity against SARS-CoV, the virus known to cause Severe Acute Respiratory Syndrome. Many of the components of Bay Laurel are found in other herb/spice oils such as Rosemary. Bay Laurel is also on the GRAS list, safe for ingestion in small amounts. As with other oils mentioned here, it can be diffused to disinfect the air in your living or office space.

This is only a short list of essential oils considered to have antiviral properties. Many studies have focused on the Herpes Simplex virus, as the efficacy of treatments is easy to evaluate. However, an in-depth look at the research abstracts available through Pub Med can give you a more complete look at up to date scientific data. A search for 'essential oil virus' currently yields 90 results. Also, as it is typically difficult for one to precisely determine the type of virus one may be attempting to eradicate, or prevent infection from, a blend of antiviral oils is often advised. Mixing oils listed here, and listed elsewhere on the web, is fun to do, and can result in a wonderful diffuser blend, or a mixture for other more intensive applications.