I can speak from experience and unless there are no nooks or hidden ridges (read the word hidden!), I wouldn't do it. We have had potato soup that smelled of Rose FO, it's quite an aquired taste, but you get used to it...
My last stickblender was plastic and it wasn't until it broke, that I realized that there were hidden nooks in it, that captured soap and held on to fragrance oils. Minute amounts, but enough to make lasagne and soup smell quite funky, no taste difference.
I bought 2 stickblenders now. A cheap one for soap making and a lovely stainless steel Krups Blender for cooking. The funny thing is, the expensive one could be used for both, it's completly sealed and stainless steel. But it's not going near the soap pot...carrot and coriander shouldn't smell funky!