Why does my nose get stuffy after being in air conditioned room? mainly in rooms with window ac units, not places with central air

? Mold allergy: Molds tend to linger more in window units/split units, which need cleaning more often, that can be a cause. Another cause can be vasomotor rhinitis, difference in temperature/atmospheric pressure would cause congestion in nasal vessels leading to stuffy nose. Keep using the saline nasal washes, try to see an ENT for evaluation if you really suffer