Immune Boost Essential Oil Blend (A Thieves-Type Blend) Immune Boost Essential Oil Blend This blend (and many similar ones over the centuries) was created based on research about four thieves in France who covered themselves with cloves, rosemary, and other aromatics while robbing plague victims. Similar oil blends have been university tested with amazing results for their cleansing, bacteria busting and mold inhibiting abilities. It is highly effective in supporting the immune system and good health.