Before investing in any treatment or air-cleaning product, most allergy experts recommend attacking the allergen, whether that involves rigorous cleaning and disinfecting or removing the source completely
That may be easier said than done, however: "If you like Fluffy the cat, you're not going to get rid of Fluffy," said Asher.
Controlling allergens may be as simple as opening a window.
"Many people should try to ventilate the house," Asher added.
Homes are better sealed these days, thus keeping many outdoor allergens like tree pollen outside, but that same tight seal can trap air inside, along with solvents, cooking odors, smoke, pet dander and other allergens.
"In truth, the air can be cleaner outside than inside," Asher said, noting that in urban areas that might not always be the case.
For people who have tried these steps and are still considering an air cleaner to control allergies, Asher recommends starting small.
"I would probably start with a room unit in the bedroom," he said. "See if your allergy does abate. Then consider a whole house unit."