i am asthmatic.
i dive every weekend. Let me tell you a true incident last year. a diver was advised by a Padi Course director not to dive that particular day as he didn't look too good , due to his asthma. He went on a dive even after that advise. he signalled to his group he was to abort , he ascended on surface his mouth frothed, he ended up DEAD by the end of the day.
the lesson to be learned. even others are asthmatic it all depends on your individual state if you can dive or not.
I have been able to control or prevent my attacks from occuring. i also have stopped taking brochodilators or any medicines as i have experienced that it's irritating and risky to be inhaling my medicines before and after a dive, irritating.
i take aparticular type of tea. and it works wonders for ME. i do not say it will work for you. It may not even work nor you may even not like it. but i assure you it is non-pharmaceutical it is just plain tea.