I.,
First let me clarify some of what you may be hearing regarding the link between sugar and asthma. ONE study was done in laboratory mice which suggested that sugar may have an affect on the amount of inflammation (one component of the asthma equation) in the mice that were studied. Also, in the study, the mice were basically given a diet that consisted of nothing but sugar. With that being said, I doubt very seriously that your grandchild is eating sugar and only sugar all day long, like the mice in the study. More studies need to be done before we can know for sure what role sugar plays in asthmatics. Also, please remember that sugar is naturally occuring in many, many things that we eat that are good for us. I believe one person mentioned below that sugar is an "environmental toxin" and that just simply is not true. It is natural substance found in our environment... we humans like to refine it... but it comes from a plant and is not a toxin. It can have toxic "effects" if we eat too much of it, though, just like anything else we might do in excess.
Also, if your grandchilds doctor prescribed antibiotics and steroids, most likely it was because he had an infection that he was trying to clear up (the antibiotic) and also to keep the inflammation under control (the steroid). I'm not a big fan of steroids, but they literally can save a person's life if you need them. It's up to the parents and the doctor to make a uniform and educated decision, weighing the pros and the cons. All that being said, I doubt very seriously that the doctor would have prescribed them unless they were necessary.
To understand asthma, you have to understand that there are two basic components that need to be treated - airway constriction and inflammation. If your grandchild is having frequent asthma attacks, then you might need to look at trying to find a medication that will prevent the asthma attack in the first place. You should also consider testing to find out if the asthma is being exacerbated by allergies (pets, pollen, dust, foods, etc.). If so, you can try to limit his exposure to those things. What you do NOT want to do (and I speak from experience) is blindly think that everything is just fine and not be informed on this subject. Children that grow up with asthma do not know what it is like to breathe normally. They can think they are fine and not have any visible signs of an asthma attack, but underneath the surface, they may have tons of inflammation that will eventually lead to scarring of the lungs (emphysema) if left untreated. At age 25, I found out I only had 40% of my lung function. My parents had great intentions, but they too wanted to go with a more "natural" approach. I now get regular treatment and my lung function is better, but it will never be 100%. This is due to years of not getting proper treatment that led to the scarring.
Bottom line: Work with your doctor and be informed. If needed, see that your grandchild gets to a physician who specializes in asthma/allergies. Make sure he has regular pulmonary function tests. I would recommend that you go to the doctor visits, also. It will really help you in understanding what you are dealing with.
Hope this helps!