Can allergies cause redeviation of septum after a septoplasty? 20 years post op, wondering is this could have affected me?

No, allergies would not result in a deviation of your nasal septum.The septum can warp or shift and therefore, redeviate after septoplasty, so that's more likely what has occurred in your situation if the septum is indeed confirmed by a nasal surgeon to be deviated at this point.

The issue may be hypertrophy of your turbinates and not the septum especially if affected by allergies.,turbinate reduction is a common procedure that could remedy that

Good Afternoon! Allergies tend to interact more with the mucosa rather than the septum and it's cartilage. Over time, the nose can change. If a deviation recurs, it could be for a number of reasons though allergies, unless causing incredible inflammation, would be less likely. Hope this helps!