Why do dogs eat their own puke?

Puke usually contains undigested food, which is appealing to your dog, even though it's disgusting to us. If throwing up relieved whatever nausea/discomfort they were experiencing, they'll likely be hungry again. Some dogs will also instinctively clean up messes in their living space, which to them means eat it up, like a mother dog eating the waste of her litter of puppies.

I absolutely agree with Laura's comment above. A large percentage of the time, it's undigested food. This can also ring true for poop -- sometimes there is undigested food there, and dogs can still get nutrients from either the poop/vomit.

My little guy used to do it when he would throw up in the house, out of fear that we would be upset at him.

If this is happening often, you may want to see if there is a problem with the type of diet you have him on.

Also, usually when dogs throw up, they eat it to hide it (almost like embarrassment). Instead of making a big deal out of your dog throwing up, talk to them, pet them, and quickly clean it up.

My dog will occasionally throw up because she is dehydrated, so be sure to get them fresh water. Another issue is eating too fast, which is when there is whole pieces of food in the vomit, and Laura is spot on when it comes to this!