Diabetes affects our blood vessels and nerves and therefore can affect any part of the body. However, certain parts of our body are affected more than other parts.
I don't think dogwoods have (much?) scent, maybe just lightly floral. The white petally looking things are not actually petals they are bracts, like a poinsettia has. There's something called an English dogwood that is very fragrant, but it isn't a true dogwood and is also known as mock orange. Bradford pears have a smell that this author described as sweaty socks, so if your tree doesn't smell very good that's probably it: http://www.gardenguides.com/106133-dogw ...
Once they bear fruit, several of the trees together will produce a strong enough citrus smell to be unpleasant to dogs. The smell of lemon, grapefruit and orange are the most distasteful. If you want only one or two trees, you can pick the fruit and scatter the peels to repel both cats and dogs.