Gizmo was just diagnosed with the same thing on Sunday. Same thing he would throw up and then eventually had blood in his stool. Hes on flagyl ( Metronidazole) & Cephalexin. Poor guy we have no idea where this came from. I think its from a recent 3 hours car ride from Los Angeles to San Diego... but its scary to know that we cant prevent it. Our vet did say to switch Gizmo to a new protein diet. Funny thing is Gizmo is also 3.5 pounds just like your baby and hes also 1.5 years old! Crazy!
It could defeinitly be a food allergy with your baby thats why she is constantly licking. Hair can cause a blockage and hair can not be digested by the stomach. Gizmo does get really dry skin during the winter and would lick himself. My mom has this oatmeal shampoo that i use on him and it seems to work well. I am wondering if thats whats going on with your baby. Or it could possibly be a food allergy. I know a common food allergy with dogs is grains. Gizmo is on Fromm and its grain free. I dont think that Iams is grain free. I hope you can figure it out! Its definitly a scary thing and i completely understand what your going through
Heres an article that i read today i thought it was informative!
Hemorrhagic Gastroenteritis in Dogs - Whole Dog Journal Article