Advice on vacuums if you have allergies
HEPA filter or anti-allergy filter
A HEPA filter or anti-allergy filter is an exhaust filter that keeps the re-emission of your vacuum clean. The filter blocks all of the dust particles, pollen, and other allergens, so they aren't expelled back into the room. When you're suffering from allergies, it's advisable to use a vacuum with a special anti-allergy filter or a HEPA 13, HEPA 14, or HEPA 15 filter. These filters block 99.95% and 99.995% of all dust particles, respectively. This filter needs to be replaced every 6 months for the best result.
It's not just dust that causes problems when you're suffering from allergies. A loyal canine can be loads of fun, but it can also be a cause of lots of stray hairs. Not every vacuum is suitable for these stiff pet hairs. If you'd like more information on what you need to pay attention to when keeping pets when purchasing a vacuum, make sure to read the advice article.
With bag vs. without a bag
If you're really allergic to dust, I recommend choosing a vacuum with bag. Replacing the dust bag is a lot more hygienic than emptying a dust container. In addition, a lot of dust is released when emptying the dust container, which isn't convenient if you're sensitive to it.