Essential oils are extracted from a variety of plants, including trees, shrubs, flowers, grasses, herbs and fruits. The oils extracted are concentrated in different parts of the plant. Many essential oils are known to exert antimicrobial activity, but the mechanism of action is often not entirely understood. Membrane disruption by the lipophilic constituents may be involved in this mechanism. An important characteristic of essential oils and their constituents is the hydrophobicity, which enables them to partition in the lipids of bacterial cell membrane and mitochondria thus disturbing the structures and rendering them more permeable. The chemical components of essential oils are analyzed by gas chromatography mass spectrometry