Aerokat Chamber
The first thing you should try when your cat is diagnosed with Feline Asthma is the Aerokat Chamber. This allows you to deliver aerosol medication in an effective way. It will take some time for them to get used to it, but if you can get them comfortable with it, this product can help tremendously.
Air Purifier
Buy an air purifier. The one we use is the LEVOIT Vital 100. This one seems to do the trick and the filters last a long time. However, you do not need to purchase this one, as there are many other options out there. You will start to notice if you turn it off, or if there is a power outage, your cat's symptoms will return. Running this daily will help to improve the quality of air in your home, removing any possible allergens and preventing any possible asthma attacks that could occur.
Healty Cat Foods
You can find these many places including Chewy, Amazon, and your local pet store. These will be much more expensive than your Friskies or Fancy Feast, however, they will not contain many of the potential allergens. For example, many cats are allergic to chicken. Chicken and chicken meal are the number one ingredient in many of the leading cat food brands. Try to use wet, and something with a short ingredient list. Alternate meats such as Venison, Lamb, Goat etc. will provide your cat with a nice change. These animals aren't as pumped full of chemicals as other more prevalent meats. Fish can also lead to issues, mostly due to many of them containing high amounts of mercury.