That's called aromatherapy.
Aromatherapy is the use of aroma to bring about a physiological, psychological and emotional change.
Although we normally associate aromatherapy with scents of exotic plants and flowers used to soothe, calm and comfort, the healing effects of aromatherapy can be found in your backyard. Basil has been praised for centuries for its ability to ease tension and promote alertness. Chrysanthemums are noted in Chinese traditional medicine for their effect in combating fever and headaches. Cinnamon can be used as a stimulant to treat fatigue and depression. Eucalyptus is famous for its alleviating effects for colds, flu and bronchial congestion.