Where the dust actually comes from
Hay itself, sitting quietly in a rack, releases very little. The dust billows out at the handling moments: tearing a serving off a compressed bale, shaking a flake loose, tipping the dregs of a bag, and sweeping up around the cage. That is good news, because moments can be moved, timed and assigned to particular people in a way that "dusty hay" in general cannot. It also means the fix is mostly about routine design rather than expensive equipment. One more source is easy to miss: hay stored open in a warm room sheds fine particles into that room's air all day, so where the bale lives matters as much as how you serve it.
Change how the hay is stored and served
Store opened hay sealed — a lidded storage box or the bag rolled and clipped shut — in a hallway cupboard, garage or utility space rather than a bedroom or the corner of the living room. Portion it at the point of storage: shake each serving out there, ideally outdoors or over the bin, so the cloud of dust happens away from living space, then carry the loosened hay to the cage in a basket or hay bag. Quality varies enormously between batches and suppliers; dust-extracted hay is sold precisely for this situation, and if a delivery arrives visibly powdery when shaken, treat that as the wrong hay for your household rather than a fact of life, since rabbits and guinea pigs breathing dust all day do not thrive either. Serve hay in a rack or a contained hay area rather than scattered, so less of it gets trampled into bedding and kicked up.
Keep the pet's air and the person's air apart
The allergic family member's bedroom is the one room to defend absolutely — no cage, no hay storage, no shaking out clothes worn for a big cage clean in there. Cage cleaning is the dustiest job of the week, so schedule deep cleans when the allergic person is out, ventilate the room during and after, and let whoever cleaned change their top and wash hands and forearms before hugs and sofas. A vacuum pass with a proper filter around the cage area after cleaning catches what settled. Running an air purifier in the cage room during the day takes the edge off the background level between cleans.
If symptoms flare anyway
Track the pattern before changing everything at once: if symptoms spike on cleaning day, the routine needs tightening; if they build through the week, storage or background levels are the leak. Asthma that worsens despite a careful routine is a conversation for the person's own doctor, who may want to test whether hay, bedding or animal dander is the main trigger — each has different fixes, and guessing wrong wastes effort. KinsLe's Family Sharing keeps the low-dust method from depending on one person's memory: the shared profile spells out who shakes out the hay, where it is stored and what happens on cleaning day, so a well-meaning relative does not undo the system by helpfully fluffing a bale in the kitchen.