I friend of mine ho went through weight loss surgery (RNY) had that problem, and it turned out she was allergic to one of the sugars in her protein shakes.
It could also be something as simple as a new soap or laundry detergent though.

A good way to get rid of problem protein shakes and bars is to take them to support group with snack bags. Everyone wants to try different brands and everyone will love you for sharing a taste. It is show and tell and share at my monthly support group. We chop a protein bar into 10-12 bits so everyone can taste. We bring wrappers of stuff we love and people take snaps or scan the barcode with their phones. We talk about our best bargains online and local. We share recipes and tricks for success. It is a total blast!