A dog stops eating for many different reasons, but it is important to have the dog checked by a vet to rule out any health issues if it does not start eating again within a couple of days. Owners must inform vets of any vaccines their pets have recently received as vaccines also affect appetite, according to WebMD. Other reasons include unfamiliar settings or changes in diet.
If a pet is eating fine at home but suddenly quits eating when on a road trip, it may be experiencing motion sickness or is uncomfortable with the new setting. Introducing a new pet or person into the home also makes some pets nervous about eating, especially if the new addition spends too much time around the pet's food bowl. WebMD indicates pets adjust and begin eating normally again once they feel comfortable.
While humans often like variety in their diet, introducing a pet to a new brand of dog food causes gastric upset. Purina recommends slowly introducing new food by mixing it with the old and increasing proportions over a week. Other pets seek their own variety, getting food out of the neighbor's garbage can or by seeking too many treats from their owner. Eliminate access to other food sources and limit the treats the dog receives.