When choosing the best air purifier for allergies, look for a true HEPA filter, a CADR rating that matches the size of your room, and a unit that can run quietly enough for daily use. True HEPA filtration is important because it captures common allergens such as pollen, dust, pet dander, and mold spores, while a properly sized CADR ensures the purifier can clean the air effectively in your space. It also helps to consider filter replacement costs, noise level, and where you plan to place it, since a purifier works best when it has room to circulate air freely. For bedrooms and other allergy-prone spaces, a reliable, easy-to-maintain purifier is usually the smartest choice.