We just discussed the reasons why some people prefer bagless vacuums over bagged vacuums. But are bagless ones the right choice for people with allergies?
There are major disadvantages for allergy sufferers when it comes to bagless vacuums. The process of emptying the dust cup is by no means a clean or tidy affair. As soon as you remove a dust cup from a bagless vacuum, the uncovered cup releases dust and dirt back into the air. If you empty it into a bag, you're going to create a dust cloud as you dump it. If you empty the dust cup outside, you better stand upwind, or you'll end up covered in the very dirt you just removed from your rugs and carpet.
Sometimes the vacuumed debris gets stuck in the bottom of the cup, requiring you to pry it loose. This, too, is likely to cause dispersal of the allergens over yourself or your home, and shines a light on the convenience of just being able to toss a bag of dust into the trash as you do with a bagged vacuum.
Many vacuums sold today offer a relatively new feature: HEPA (High Efficiency Particulate Air) filters. These filters are constructed of tightly interwoven fibers (often fiberglass) that trap tiny particles that other vacuums often don't catch. HEPA filters are able to trap particles as small as 0.3 microns, but only when properly installed by the manufacturer. HEPA filters require good engineering and strong seals, so that dust and dirt (and the air that carries it) won't take the path of least resistance: a crack in a seal of the vacuum itself. Additionally, vacuums with HEPA filters require more suction power than they do without HEPA filters, so if the filter has been arbitrarily added to an otherwise low-end model, the resulting suction power will leave much to be desired.
For the person with allergies, the best bet is probably a quality, high-end bagged vacuum with a HEPA filter. While the upfront price and the cost of maintenance will be higher (HEPA filters will need replacing every year or so), the results will be worth it. You'll rid your house of more allergens than with any other type of vacuum, and you'll be less exposed to those allergens when handling the vacuum and changing bags.
For lots more information on vacuums and allergies, see the next page.