You might want to read some of the articles available on the web rather than have personal lists of possible causes. After all, each person may be different.
I have never associated my allergies with high blood sugar per se, but know that too much sugar in the diet, including carbs that metabolize into sugar in the body, will make staying awake in the afternoon almost impossible, for starters. Long term problems, from my study, including hearing loss, eye damage, lack of ability to control weight, and yes, dementia, and possibly Alzheimers. Hyperglycemia is an unbalanced diet, both in calories and good nutrition. It is often associated with obesity and heart problems as well, and shortens lifespan. Don't take my word for it, get to reading and studying the facts. Dorisena