Garlic oil is prepared using steam distillation, whereby crushed garlic is steamed with the resultant condensation containing the oil. Garlic oil contains volatile sulfur compounds such as diallyl disulfide, which is the "most abundant constituent" of essential garlic oil. Steam-distilled garlic oil has a pungent odour and a yellow-brownish coloration. Its odor has been attributed to the presence of diallyl disulfide. To produce around 1 g of pure steam-distilled garlic oil, around 500 g garlic is required. Steam-distilled garlic oil has around 900 times the strength of fresh garlic, and around 200 times the strength of dehydrated garlic.

 

        Garlic oil is used as a nutritional supplement, and is sometimes purveyed in the form of capsules, which may be diluted with other ingredients. Some commercial preparations are produced with various levels of dilution, such as a preparation that contains 10% garlic oil. Herbal folklore holds that garlic oil has antifungal and antibiotic properties, but there is no high-quality clinical research to indicate such effects exist. It is also purveyed in health food stores as a digestive aid. It can also be used as an insecticide, whereby it is diluted with water and sprayed on plants.