The dog's refusal to eat and vomiting thick foam may be caused by gastrointestinal disease, food poisoning, or accidental ingestion of foreign objects. It needs to be taken to the pet hospital for examination and treatment as soon as possible. In addition to these infectious diseases such as canine distemper and canine parvovirus, dogs can also cause vomiting, diarrhea and other symptoms. They need to eat and drink first, and then go to the hospital for examination and symptomatic treatment to prevent the condition from becoming more serious.