It depends on the triggers and the severity.
Mine is triggered by animal fur but is mild and I have never had any trouble with it (or any attacks, even when in contact with animals). I exercise regularly and if anything am fitter than many people I know.
I hold a class 1 after some very thorough checks by the CAA. It appears however that this still isn't good enough for some airlines who want superman (woman).
Am I wasting my time and money because of something I cannot help yet which doesn't cause me any problems ? Only time will tell, but I have overcome many obstacles to get to where I am now and I wont be beaten by Asthma or anything else.
Speak to the CAA on the phone. Their medical team are very helpful.
Good luck.
NH