protein shakes causing nausea

could the protein shakes be causing allergy drainage?

I don't know but I heard that a great protein powder with no taste and is hypoallergenic is pea. It is made from peas 

I felt nauseous with every protein drink up till recently and still can't handle even a small portion of a protein bar.  Post op I noticed a clear nasal drip after drinking or eating anything.  It stops a few minutes after finishing my meal.  I mentioned this to friends and have had several tell me that they do this even though they have never had WLS.  I just found it odd that I started this issue after WLS. 

I've also gone onto pea protein because I can't stomach any of the ones in my cupboard( pre surgery I really though people were carrying on when they wrote this- I ate those thoughts!) there's no funky smell and I can drink it without gagging and shuddering.