Why does garlic make your breath smell?

When garlic is chopped or crushed, an enzyme converts a compound called alliin into allicin, which quickly breaks down into several sulphur compounds. Most are broken down in the mouth and gut, but allyl methyl sulphide is not easily digested. It is absorbed into the bloodstream and released through the lungs and skin, so garlic breath can last for hours, even after brushing. A 2016 study from Ohio State University found that raw apple, lettuce and mint reduced garlic breath compounds, likely because their enzymes and phenolic compounds break them down.