It is also possible to have allergy like symptoms, especially a runny, stuffy nose without having an allergic reaction. It's called (creatively...) non allergic rhinitis - most of the same symptoms, just without an immune response. It has a number of causes from hormones to mechanical irritants.

more info here - http://www.webmd.com/a-to-z-guides/nonallergic-rhinitis

It is quite surprising that your allergy doc wouldn't know about this though...