An essential oil is a liquid that is generally distilled from the stems, leaves, seeds, roots or flowers of the plant. The commonly used essential oils used are lavender, tea tree, orange, lemon, peppermint, cornmint, and others. These oils are antibacterial, antiviral, antifungal, and antimicrobial. They by-pass the digestive system easily and thus are beneficial for people with poor digestion/assimilation. Moreover, essential oils are highly oxygenating and are suitable for infants since they cannot swallow tablets and capsules. The potential danger of an essential oil is sometimes relative to its grade or level of purity, and sometimes related to the toxicity of specific chemical components of the oil. Many essential oils are designed exclusively for their aroma-therapeutic quality; these essential oils generally should not be applied directly to the skin in their "neat" or undiluted form. Some can cause severe irritation, provoke an allergic reaction and, over time, prove hepatotoxic. Certain essential oils, including many of the citrus peel oils, are photosensitizers, increasing the skin's vulnerability to sunlight. Even certain therapeutic grade oils can pose potential threats to individuals with epilepsy and to pregnant women.