Many of these foods affect dogs in the same way that they affect humans, but because dogs are considerably smaller than humans, it takes much less of a substance to create a corresponding negative effect in dogs. A prime example is alcohol. Drinking too much can have fatal effects on a human, but most people don’t realize that a very small amount of beer, wine, or liquor can do the same to dogs, especially smaller breeds. Other foods, such as avocado, only become poisonous to dogs in large amounts. This is not to say that you should start feeding guacamole to your pet — it’s just not nearly as dangerous as macadamia nuts or caffeine.