Let him eat some grass
Let the dog eat some fresh gras outside. They prefer some wetter long grasses. It settles their stomach and helps with digestion. Dogs naturally know what kind of grasses to avoid if your concerned.
I also would avoid the aspirin. It could irratate the stomach somewhat if it isn't coated aspirin. You can also try some pepto bismal if it is stomach upset.
I would suspect side effects from not taking regular medication, a blockage, or just a change in environment. Keep an eye on the food too. Give some canned food and make sure the dry dog food is good. Canned food is higher in calories and may help keep his strength up till this passes.
Scooby, Shaggy the "Dogs", Ms. Thang the "Cat" and introducing Measley Weasle "The Ferret".
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