Frankincense is derived from the trees of the genus Boswellia and is often used in incense and perfumes.
It has traditionally been valued for its effect on the respiratory system, and has been used to treat coughs, catarrh, bronchitis, and asthma.
Menthol is an extract of peppermint. When inhaled, it creates a cooling sensation that can soothe or numb a scratchy throat.
A 2013 study suggests that when a healthy person uses peppermint oil, it can help to relax the muscles of the windpipe, known as the bronchial muscles. This may explain why this essential oil can ease breathing in people with coughs.