asthma and arnica

I have a question about my husband's health. He has asthma. From age 5-12 he drank about 4 liters of powdered milk every day and lived a VERY busy life. At around 10 years old he had bouts of sneezing, so much that it exhausted him and his breathing began getting more and more labored. To speak was an effort. He says that he dreaded the night because all was quiet, and he still couldn't breathe or sleep. For years he slept sitting up to help the breathing. He was not allowed to eat cold foods, i.e. ice cream, watermelon, cold drinks, and no milk products, etc.

This was in Taipei. Then at 17 he moved to New Zealand. Just moving to another, cleaner place helped his asthma, and he learned a few techniques of mind over body to help with the asthma. For example he would pump his arms up and down for 1 minute breathing strongly. This would help convince his brain and body that he could breathe. He also lived and worked in Australia for 2 years at the age of 25. There his health was the best in his life. He exercised and his breathing and lungs felt normal. Now in the south island of New Zealand his health seems to be regressing. He's taking his asthma inhaler more now. He gets bouts of exhausting sneezing. He always has a running nose and a cough with something slightly gurgly down in the lungs. He prefers not doing things out of doors in the cold or wind.

I was wondering if you were familiar with this and had any suggestions on how to strengthen his body. Based on his moving to New Zealand and improving a little and his experience in Australia of not having any problems, it seems like he can get over it. However, I have heard that people with asthma get scar tissue in their lungs that never heals but worsens over the years. I tried to give enough detail to help you accurately consider it. If you need to know anything else please ask. Thank you.