While these two seasoning blends are often compared, they are in fact very different. Cajun seasoning mix originated in Louisiana, New Orleans in the United States, the home of Cajun cuisine. It's robust and savoury and features a hint of heat thanks to the addition of cayenne pepper. Old Bay comes from the Chesapeake Bay region of the United States. It's most often used in seafood dishes and is made with celery salt, mustard, paprika, bay leaf, red pepper flakes, and a handful of other spices. It's quite zesty and spicy due to the red pepper flakes.