What difference between pickling spice and whole mixed allspice?
No it cannot, as they are both different things.
Mixed Spice it a blend of spices, (cinnamon, ginger, nutmeg,
cloves, corriander seed, cassia, allspice).
Allspice comes from the dried, unripe berry of a pimento tree.
It looks a little like a larger peppercorn... kinda.