Nut allergies present in vegetable shortening from Frying pecans or does it dissipate?
Depends on exactly how sensitive the allergic person is, but there is some protein/allergen transfer. So there is an allergy risk. (Depends on the particular person whether it'll cause harm or not—but there are reported cases where it has). To avoid transfer, you need to thoroughly clean out the fryer/pan/etc. and use fresh shortening.
See, for example, http://www.foodallergy.org/file/cross-contact-poster-set2016.pdf
I had a friend with fish allergies, and he ran into big problems when eating at a bar where the french fries came out of the same fryer that had previously been used for fish.
I'd say, yes, there's a good chance of cross-contamination.