I know someone who has eosinophilic esophagitis. In his case, it's being treated as an autoimmune disease, as opposed to a chronic allergic condition. Never heard of it in relation to AS or NSAIDs.
perhaps found something here: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1002150/pdf/annrheumd00284-0051.pdf
diagnosed with AS April 2018, starting with cervical pain/stiffness; Aug 2018 enthesitis/bursitis left Achilles
diagnosed with AAU Nov 2017 (7 flares so far)
Sulfasalazine 3g 08.2018-05.2019 (worked for AAU & peripheral)
Supplements:C/D, omega 3/Probiotic/ Mediterranean NSD/curcumin
Predonisone in case of another AAU flare