When people give their dogs a treat, it's frequently the same kind of things that they enjoy eating and drinking themselves. After all, what harm can it do occasionally? Sadly, although you mean it as a reward it can often make your dog unwell. A dog's digestive system is very different to that of a human's and the wrong food can cause anything from short-term discomfort to serious long-term harm.
A quick look at a list of what you might think is usually OK will reveal things you shouldn't be offering your faithful friend at all. What's more you have to be strict with yourself. Your dog trusts you completely and believes that anything you offer is safe, simply because it comes from you.
Milk Products
Although all mammals have milk at first, they grow out of it eventually. Your canine friend quickly develops to a point where they can't actually process the lactose (a kind of sugar) which is present in all dairy product. In the stomach that sugar begins to ferment, becoming a form of alcohol. Your dog is likely to suffer stomach pain and possibly diarrhoea.
Cheese and yogurt also contain lactose and although you can find lactose-free products (because some people are lactose intolerant), why give your pet something that has no benefit? If you want to give your dog a drink they would prefer plain water!
Fruit
Although your dog is a carnivore (nature gave them those teeth for cutting through meat) many dog foods contain vegetables as well, primarily for added vitamins and minerals. If you buy dog food from a reputable manufacturer and It contains vegetables, that's fine. The same is not true of fruit.
While the vitamin C in fruit is beneficial, most fruit also contains citric acid which is likely to cause your dog intestinal discomfort. Bananas contain potassium which in large amounts can cause heart problems Raisins and grapes have recently been linked to potential kidney failure. Nuts must also be included in this section because, just like in some people, they can cause surprisingly violent and dangerous reactions.
