In my personal experience, I've noticed more dogs tend to have a problem handling pork. Not so much ALLERGIES, but just a general intolerance that caused GI upset such as loose, runny stools.
The bulk of my boy's diet was always chicken, because it's the cheapest. They've never had a problem with it, although as I said above my older boy has never handled pork well.
I did get a very large box of frozen chicken necks for free off craigslist one time after a woman discovered her dobermann was allergic to it.
As others have suggested, simply try NOT feeding the chicken for a few weeks, and see how it goes.