Buy a HEPA filter-equipped purifier, such as the Honeywell 50250 Enviracaire, for about $175. The cheaper ionizing models do more harm than good, says allergy and immunology expert Thomas Selvaggi, MD. "They create ozone, which can damage lungs and elevate blood pressure."
Why it's worth the splurge: Air purifiers aren't musts for everyone, but research suggests they help asthma and allergy sufferers breathe easier.
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