Thirty-six persistent allergic rhinitis (PAR) sufferers were studied, to both compare and correlate 15 minute response to nasal xylometazoline (XYLO) with 28 day response to nasal mometasone furoate (MF). 0.1% XYLO (1 spray each nostril) response was measured on two occasions, then a randomised double blind cross-over comparison of MF (200 mcg daily) to placebo conducted. Outcomes were peak nasal inspiratoly flow (PNIF), nasal forced inspiratory volume in one second (nFIV1) and nasal blockage score (NBS) improvements. Thirty-one participants completed per protocol. Within subject standard deviation for percentage improvement to XYLO was 26.0 for PNIF and 25.2 for nFIV1. Median % improvement (95%CI) in PNIF for XYLO vs. MF was 20.0 (11.4 to 31.0) vs. 9.6 (3.2 to 15.8) and in nFIV1 was 17.8 (10.0 to 28.1) vs. 3.3 (-4.3 to 19.1). XYLO effects were greater than MF (p<0.05) for PNIF, nFIV1 and NBS. There was no significant correlation of MF to XYLO improvements in PNIF, nFIV1 or NBS. In conclusion, acute reversibility to XYLO showed poor repeatability and XYLO reversibility is not predictive of decongestant response to nasal corticosteroid. XYLO was a stronger decongestant than MF but rhinitis medicamentosa still precludes any preference for long term XYLO therapy at this time.