Helen Nagle-Smith experiences essential oils  as colours. Elizabeth Ashley hears fragrances as musical notes.

The artist Kandinsky heard the colours of his paintings as music and Kanye West often describes how he sees his music in colour.

In 1862, the English perfumer, Septimus Piesse, first coined the term, of how for him, scent and sound were intrinsically linked, and this was reflected in the beautiful fragrances he created. Smound

Incidence is hard to measure with suggestions ranging from 1 in every 23 people to 1 in every 2000. Whist true synaesthesia is thought to probably be congenital; research suggests that other non-synaesthetes may be able to develop certain traits with training.

Learning to develop a cross sensory appreciation of an essential oil brings aromatherapy to life. It deepens ones understanding of an oil's nature, and shows how its nuances might affect our personalities and physicality and how other people might…