Hello, my name is***** and I have over 20 years of experience as a veterinarian.
I am very sorry to hear about your pup Fancy's episodes of eating leaves and gagging and swallowing. ,
This sort of behavior where the dog acts uncomfortable means it is likely that the pup is experiencing some reflux or abnormal motility, or painful intestinal spasms that are more than the usual. In severe cases this can be linked to pancreatitis which is a painful inflammation of the pancreas leading to increased enzyme leakage.
Some dogs like the taste of grass or leaves, but also many dogs with nausea or gastroesophageal acid reflux eat grass or foreign material to make themselves vomit. They will often swallow repeatedly and lick things trying to soothe their nausea and acid burn. If they can rid themselves of whatever is irritating their stomach that way then all is good. But when they continue to be uncomfortable then we need to stop them from eating any more plant material. It becomes a vicious cycle where more plant material irritates their stomach, and stomach acid refluxes and burns their esophagus, and the worse they feel, so they try to eat more plants.
Possible causes of nausea and abdominal pain include a change in diet, dietary sensitivities or allergies, or eating things that they should not like too many fatty table scraps or garbage, bones etc. Addison's which is a poorly functioning adrenal gland is another possibility for waxing and waning vomiting and nausea. Metabolic organ failures (kidney or liver disease), pancreatitis, inflammatory bowel disease or even infiltrative cancers are possible causes as well.
Has she eaten anything she should not have recently (toy pieces, bones, garbage)?
Any changes in food or treats?
When she has these episodes I wouldn't let her eat plants. You can give her acid reducers to try and settle her stomach. Either:
1) Pepcid-ac (famotidine) at a dose of one 10mg tablet per 20 to 40 pounds of body weight every 12 hours.
2) Prilosec (omeprazole) at a dose of one 20mg tablet per 40 to 80 pounds of body weight every 24 hours.
These will reduce stomach acid and should help settle her stomach. These can be used long term if necessary as they are very safe.
I'd also pick up her food and water for now. A couple hours after one of the acid reducers you can offer small amounts of water or ice cubes to lick.
No food for 12 hours. Small amounts of water only.
After her food fast then start a bland diet of 1/3 boiled, lean hamburger (or boiled, white, skinless chicken) and 2/3 boiled white rice. Give small meals several times a day. Feed the bland diet for several days, then start mixing in her regular diet and slowly convert her back.
If her nausea and abdominal pain continues then she may need injectable medication from her veterinarian to get her stomach upset under control.
So watch her for continued symptoms even with the acid reducers, blood in her stool or vomit or a fever (more than 103.5F rectally), a tense painful belly or lack of appetite after her food fast. If any of those occur it is time to seek hands on veterinary care.
Since this has been a repeated problem for her consider whether she has been getting different treats or lots of table food, or have you been feeding a different diet?
If you go back to the original food, stop table food and treats and her nausea continues even with the acid reducers, fast and bland diet then you may wish to consider using a pet store sensitive stomach diet like those made by Science Diet or Royal Canin brands, or a prescription low irritant food, like Hills i/d or Purina Veterinary Diets EN. Some dogs benefit from a hypoallergenic food such as Hills z/d or Purina Veterinary Diets HA long term. She may have a dietary allergy or a sensitive stomach. It would also be a good idea to have blood tests done as well to make sure there isn't an underlying metabolic problem like early organ failure, pancreatitis or Addison's disease present.
Please let me know if you have any further questions.