4 year old has bloating in face and abdomen. History of eosinophilia gastroenteritis and low muscle tone. Why is face getting bloated?

Unclear ? Do you mean the face is swollen as in angioedema? If so this is not a part of EGE but possibly from food allergy. You need to check with your pediatrician re possible malabsorption issues leading to the low muscle tone (assuming the child is physically active otherwise).