I heard about macadamia nuts before, but I didn't realize that dogs were unable to digest nuts in general. Good to know!

One thing I learned some years ago is that giving dogs shrimp shells can mess them up pretty bad. One day a few years back I was eating a ton of shrimp and throwing the shells to my dogs. They both happily gobbled them up. Within a day, both of them got bleeding scabs (weirdly) in the bony crease between their eyes and down the nose. 

It was so weird! We took them to the vet and he asked me what they had eaten. After I told him about the shrimp, he said that dogs have a strong reaction to the histamine in shellfish. I felt like a crappy dog owner, but learned my lesson after that!