You hear everywhere people talking about what’s going around, and that you are bound to catch it. Not so, if you are careful.
Dairy is responsible for most ear infections and colds, in my opinion, because it is mucus-forming. Many grains and soy products also have this effect. Grain free/dairy free would be the best preventive diet.
As far as what to add, I would determine bowel tolerance for Vitamin C and dose
everyone in your family just below that level daily. I myself take 4-5 1000 mg tablets every morning and can’t remember the last sinus infection or cold that lasted more than a day or two. Bowel tolerance is determined by starting with one pill. The next day take two. The next day take three. When it causes diarrhea, you’ve taken too much. The diarrhea will last an hour or less. One or two pills below that level is likely to be your best dose.
Detoxing helps too once you are sick. I believe the old adage, “Starve a cold, feed a fever,” and in that order. You would want to feed the fever, however,
with easily digestible foods.