Pennyroyal mint is a well known ground cover and frequently used to plant between stepping stones and around paving stones. The plant has a tendency to grow over the sides and as one would step on it, the leaves release its potent essential oils that fills the air with a fragrant fresh mint scent and this is also well known to keep away mosquitos and other insects. The leaves can also be rubbed against your skin to repel mosquitos, but caution should be taken as this can burn sensitive skin so a small test patch should first be attempted. Several articles suggest that pennyroyal mint should not be taken internally but when used in moderation, it is safe for internal use as well.