I developed asthma in my early forties.

What helped was

1) Buteyko method

2) Yogic breathing and stretching with yogic principles for eating sattvic foods, chewing thoroughly.

3) drink black coffee (opens the alveoli)

4) Buy a diffuser and use essential oils like Frankinsense, eucalyptus, peppermint, rosemary

5) Go for saunas regularly.

All these additions/smll changes combined made a big difference.

Hope this helps. x