Do Air purifiers really work? How do they work? Which one would you recommend?

Yea, the only problem is that they cost a fortune. Simply put, they give stuff in the air a negative charge so that it will attract to the positively-charged metal bars. The air is clean and once you clean the bars you can give it another go.
I think Sharper Image makes a good one. Beware, they cost a lot of money

Can Air Purifiers also remove or reduce dust? Which ones are best?

We have a Orkia(?spelling)
We have cats, dogs and smoke and after getting this thing the whole house smells clean and the dust you see in the light is not there. Nice thing about it, the cleaning cell can be cleaned with water, no re buying filters

Are air purifiers that use water as the filter medium any good?

I want to buy an air purifier and saw one one the view that uses water

Never heard of that kind. You'll have to change the water constantly, and run the risk of blowing algea and mildew around the room if you don't keep it clean.

The one by Orec looks good. Expensive, tho, but you don't have to buy filters, and it does seem to move the air around.

My kids and I have bad allergies sometimes the kids get nose bleeds from allergies. I'm thinking about buying an air purifier? I want to make sure that having one is really going to be effective. I also want to know from some of you other allergy sufferers out there, what is the best air purifier to purchase? brand? where to buy? I have researched a little but some of them are very expensive from $400.00 - $800.00. My budget is like $200. So if anyone can help please let me know and I thank you for all your answers. Wish me luck! I hope I find one soon.

Yes they help tremendously. You do not have to buy an expensive one. Call the allergist and get his/her recommendation on what to buy, Also be sure the kids use vaseline in their nostrils at night to help prevent nose bleeds. You should also consider getting rid of all of your toxic cleaners and laundry products as many of them are registered pesticides. Replace them with all natural cleaners and take the old stuff to your nearest toxic waste disposal place to get rid of them. Once you get the non toxic stuff clean your home top to bottom including the carpet and furniture with the non toxic stuff. Wash everyones clothes in the non toxic laundry products and I am sure you will see a biggggggggggg difference.

Do air purifiers really help?

With, dust, polon, odors?Which are best and affordable?

Yes, they really do, but stay away from the "Ionic Breeze" types, as they are total scams. The principle is sound, but will only work in an enclosed space, and even then will take forever to clean a 4' square box. A good hepa filter unit can do that in about 30 seconds. The best one? Buy the best you feel you can afford. Make sure it has some sort of carbon element or it will do nothing for odors. Cheers....

Why do their prices vary so much? and does brand matter? if so what is the best Brand to buy?

They're fantastic at emitting O3 or ground level ozone, a toxic substance to humans that causes inflammation of the esophagus, among many other ailments.

Frankly, I can't believe they haven't been banned from being made yet. They may kick some dust out of the air, but they cause more damage to your body than benefit. I strongly advice you to stay away from these.

Are dehumidifiers or air purifiers better for getting rid of dustmites?

Are dehumidifiers or air purifiers better for getting rid of dustmites because I heard that air purifiers only get rid of allergens that are already floating in the air and dustmite allergies are "blowed upwards in the air" only when you step on carpet or lay your head and body against the bed and pillow causing them to rise into the air.

Dehumidifyers HELP because dust mites thrive in humid areas. Air purifiers claim to help but they actually can't get to the dust mite particles because they are so heavy. They are only in the air for a very short period of time before they fall to the floor and other fabric areas.

The best thing you can do is keep your room ( most important) at the lowest possible humidity level, get dust mite covers for all your bedding, keep your room as clutter free as possible. This gives dust mites fewer places to burrow into and also less things to collect dust. You can also take an antihistamine at night which will help keep you from waking up congested.

I hope this help!

Are there home air purifiers that work? I would like to minimize dust in my space.? Are there home air purifiers that work? I would like to minimize dust in my space.?

Any HEPA filter that is rated for the space you want to use it in will remove a lot of dust. here's a bit of information on them: http://www.aircleaners.com/hepahistory.phtml

you can buy a HEPA filter at any mass merchandiser or home-improvement store. honeywell makes decent models.