Oil of Oregano to be used with caution
This from a quick search on the web:
"Oil of Oregano is steam-distilled from the flowering plant Origanum vulgare, a native to the Meditteranean region. A member of the Labiatae-mint family, it is closely related to and sometimes confused with Marjoram (Origanum majorana) and Thyme (Thymus vulgaris). Oregano Oil has a spicy, tangy and hot fragrance and a wide range of therapeutic properties, but also strong toxicity so it must be used with extreme caution. It is a strong skin and mucous membrane irritant, so it must be used in very low concentrations; and a powerful emmenagogue, so it must be avoided during pregnancy. For safety, some educators suggest using Thyme Oil or Marjoram Oil instead, although neither one may be as effective as Oregano Oil for certain treatments....
"While there are certain people who heavily promote the oral use of Oregano Oil (one man in particular on the radio), we advise extreme caution! We have heard from several people who have unfortunately burned their mouth and throat trying to take Oregano Oil orally. We suggest that you never take ANY Essential Oil orally, unless you are under the supervision of a Doctor or professional Aromatherapist who is present at the time of use. Due to its potential toxic effects if used incorrectly, be especially careful in using Oil of Oregano, and use only the very best quality Organic Oil. "
From:
http://www.lotuspress.com/lotusbrands/tiferetonline/oregano.html