asthma and diving

a friend would like to learn to dive, however they suffer from emotion induced asthma after a traumatic experience a few years ago. the asthma is controlled by the use of an inhaler. they can swim happily without suffering an attack or without requiring the use of an inhaler.

i think i'd be correct in assuming that to get the go ahead for diving then a medical referee will need to be consulted, however, would this form of asthma preclude taking a try dive?