Hi Linden,
There really isn’t any definition for “hypoallergenic” that has any specific meaning but the best protection against dust mites would be a mattress encasement (and a pillow encasement which may be even more important) regardless of the type of mattress you have. There’s more about dust mites and allergies in post #2 here.
In your budget range there really won’t be any “good quality” options … especially if it includes a foundation as well … so you will really be looking for the “best quality available” but I would keep your expectations about durability realistically low in your budget range for any memory foam mattress you are considering. I would also make sure that you know the specific return policies and know the costs involved for returning the mattress with any online purchase because no matter what the price of a mattress or the quality of the materials … if it’s not suitable for you to sleep on in terms of PPP then it would have little value to you and the costs involved in returning it may be significant in some cases.
You can see my thoughts about mattress reviews and why I believe they are not a good way to choose a mattress in post #13 here. When you are making an online purchase then the knowledge, experience, and integrity of the retailer or manufacturer you are buying from and their ability to help you make a choice that has reasonable odds of being suitable for your body type, sleeping positions, and preferences based on the “averages” of their customers along with the return or exchange policy in case you are outside the “averages” can be just as important a part of your personal value equation as the price.
The ability and reputation of the retailer in providing accurate information about their mattresses would also be a key part of your choice because some suppliers (such as FBM) have a history of not providing accurate or complete information and sometimes you may get what you believe you are ordering and sometimes you may not. For me this would be a roll of the dice and would depend on how much of a gambling spirit you have and on how comfortable you are in dealing with a company that has a history of inaccurate descriptions of their products.
This depends on the quality of the foam in the mattress but in your budget range I would have lowered expectations for any memory foam mattress … particularly if it contains memory foam that is lower than 4 lb density. While there is nothing wrong with buying low quality materials if you are OK with reduced durability and your budget doesn’t allow for better quality … it’s important to make sure that your expectations are realistic so that if in a year or two the mattress has lost it’s comfort or support that you still believe the purchase was “worth it” and that if it lasts longer than this you would consider it as a “bonus”.
I would also read post #6 here before ordering a memory foam mattress with foams that come from China (such as the Lucid).
They are correct about this and all the materials they are quoting are higher quality and more durable materials than 3 lb memory foam. Good quality polyfoam is also a more resilient material than memory foam which means that it’s more responsive and easier to move and change positions on the mattress for those that don’t like the more “in the mattress” feeling of memory foam or its tendency to sleep warmer for some people. I would personally choose high quality polyfoam over low quality memory foam but of course other people may have different “tradeoffs” or preferences than me or anyone else.
I would certainly consider the benefits of higher quality “non memory foam” materials if I was in your budget range.
Phoenix