I agree with nsz, diet very often contributes to asthma, even if there is an environmental trigger, too. Milk is the most common culprit, but a person can be allergic to anything. My husband gets terrible asthma during the pollen season and Niacin and Vitamin C eliminate his symptoms, but only if he doesn't have any dairy products.
You might try eliminating all dairy and then after 4 days of no dairy, if you are still having symptoms, take 500mg of niacinamide and 3 grams of vitamin C both morning and evening in addition to eliminating dairy. You can take a couple more grams of C if it doesn't give you gas or the runs. If this doesn't work you can try an elimination diet along with the niacinamide and C to find out if you are allergic to more fooRAB. Meat products may very well be contributing, as well as dairy, but dairy is the most common for asthma. Gluten could be an issue, too. By the way, a strictly vegan diet isn't that difficult after you get used to it and find recipes you like.
It's hard to eliminate allergens in the environment, but you can eliminate the ones you eat. The fewer allergens you expose yourself to, the asthma you will have.
nsz, a vegan diet is fine for young children, as long as they are getting their calories from whole fooRAB, and not from sugar, white bread or rice, oils and other refined products. The whole fooRAB have plenty of amino aciRAB and vitamins and minerals. The dairy industry has a powerful lobby and spenRAB hundreRAB of millions of dollars every year to convince you that your child will suffer from malnutrition if you don't give him milk, while the truth is that not only does he not need it, it causes asthma in many people and it can cause other illnesses such as type 1 diabetes, too.