help for a friend

HI all. A friend of mine just found out her 2 year old has asthma. she had been around and around with doctors. they couldn't figure out why he was always sick. so after months of being sick they confirmed he had asthma. I know very little about natural cures for a little one. Hoping you all had some good advice or some ideas of good first steps to take at this point. shes wondring if it's something he's eating that caused the problems...

Please let me know...thank you jada!!!