garlic extract (Allium sativum) is antiseptic and bactericide. It is sometimes externally applied in ointments and lotions to reduce hard swellings and to treat problem skin (acne, for example). The active properties of garlic depend on a pungent, volatile, essential oil that is obtained by distillation with water. This oil is an allyl sulfide found in the onion family, and it is rich in sulfur but contains no oxygen. The common garlic is included in the same group of plants as the onion.