staying away from a substance that causes an allergic reaction.
for avoiding (some) allergens:
when possible: wall-to-wall carpet, Venetian blinds, down-filled
blankets or pillows, closets filled with clothes.
bedding, curtains, and clothing often and in hot water to eliminate
bedding in dust covers when possible.
conditioning instead of opening the windows.
putting a dehumidifier in damp areas of the home, but remember to
clean it often.
masks when working in the yard.
vacation to the sea shore during the heaviest part of the pollen
will also have suggestions for avoiding the allergens that cause