Asthma sufferer needs help.

Hello out there,

I have a good friend who suffers badly from Astma. He's been on steroids but these have taken thier toll and he's now warned to come off them slowly. Is there anything out there that he can use in it's place - He is immune to Ventoline and it's triggered by stress and alergies. Any knowledge of alternative remedies would be appreciated also. Anybody had results with ionisers.