My dog won't eat the food she likes?

Dogs don't exactly get tired of their food. In fact, mines loves his sooo much that at first, he ate them as treats. Is it possible that maybe that food is old or expired? I would call my vet. on this one, as it could be something a little bit serious. Though, she could just be in stress, in heat, upset stomach, or if the weather is too warm , she might stop eating for a few days. But, unless your vet, gives you the OK, don't switch her food, as this may upset her stomach more. Dogs are not stupid, so if food is available, she wont starve herself. Don't sweat it, but if this continues for much longer, then i would consult your vet., as something serious could be wrong.