triggers

My husband has been diagnosed with late onset asthma...2 years ago.

This summer he spent a couple of days in hospital for assessment. He has seen a specialist who tells him that his asthma could be caused by up to 2000 different triggers and that it is up to him to find which it is.

He has had tests which have ruled out dust, fungi spores and white spirits.

His medication is Singulair 10 mg daily - Uniphyllin 200mg twice daily - Symbicort up to 12 doses a day. Every three/four weeks since July he has had to have oral steroids for 7 days.

His asthma is clearly not controlled properly and he is awaiting another appointment with specialist.

Any advice? How can we find the triggers?

Thanks