Japanese Mint (Mentha haplocalyx) is a distinct mint species separate from peppermint and spearmint. It contains high levels of menthol. Most supplements standardize its volatile oil content.
People traditionally take it to ease digestive discomfort and reduce occasional bloating or gas. The menthol delivers a cooling effect that can relieve temporary nasal stuffiness when you inhale it with steam.
You can buy the dried herb for tea, a liquid extract, or capsules. Some people use the essential oil for aromatherapy or to cool the skin. Internal use almost always sticks to tea or extracts.
Never swallow pure essential oil without professional oversight. Undiluted oils can be toxic. Mint often aggravates symptoms in people with gastroesophageal reflux disease (GERD). If you are pregnant or nursing, ask a professional before using concentrated extracts.