In addition to dust-mite allergies, our household also suffers from overlapping seasonal allergies as well as contact skin allergies. To back up Diane B, I wonder what food sensitivities your daughter also has, if any? We were told when my oldest was a baby and had both eczema and food allergies that it was fairly certain she would have respiratory allergies, too - if not asthma. These things often travel together.
For the dust mites:
We have covered all of the mattresses and bed pillows in the house. The pillows in the living room have covers that can be removed and washed, in hot water - just like the bedsheets and blankets. We don't have heavy comforters that can't be washed, and spare blankets and pillows are in dust-proof bags when they are stored. Stuffed animals were culled down, and the rest get washed, too (or put in the freezer, in the case of those with batteries or music boxes). The curtains in the kids' rooms and the fabric shower curtain are all machine-washable, too, and the carpet steamer has an attachment that works on the other shades in the house.
It's counter-intuitive, but we only vacuum once a week. The vacuum - no matter how good it is - stirs up almost as many allergens as it removes, so frequent vacuuming can actually make things worse. (Ever notice how it seems like you need to dust after you vacuum?) So I also try to vacuum when my husband or daughter are not in the room, at least. Pulling out the carpet is on our wish-list, but it's prohibitively expensive, so we pay careful attention to the vacuuming schedule. (The living room furniture gets vacuumed, too.)
We have anti-allergen filters on the A/C unit, that get changed regularly. We also have several live ferns to clean the air naturally (even if just a little bit) and add to the humidity in the house. All of the bedrooms also have cool mist humidifiers.
For other allergies:
We have found that washing hair EVERY DAY before bed during the peak allergy seasons helps a lot. The allergens settle in your hair during the day, and it really does help to wash them out before you take all that to bed with you.
Windows stay closed during the peak of the allergy seasons. Coats, hats, and shoes stay outside in the garage.
We've also found that we sleep better when we use unscented laundry detergent and no fabric softener (substitute vinegar - works like a charm). No one in the house is necessarily allergic to these things, but they can aggravate allergies in people who already have sensitivities.
And nix the anti-bacterial soaps. Allergies are your immune system going nuts over something that's not really a threat. So you have to give it real (but minor) things to worry about.
The symptoms we have on bad high allergy days are stuffy heads, sneezing, runny noses, aching sinuses (in my case, my teeth hurt, too - I have deep roots that extend into my sinus cavities, so inflamed sinuses = painful teeth), swollen eyes, headaches, post-nasal drip and the sore throats that come with it. Sometimes a cough, depending on the length and severity of the sinus drainage. (Lethargy may or may not count - since it's difficult to sleep with all of the other junk, it might just be a side effect rather than an actual symptom.) We can keep our symptoms to a minimum with all of this, but during the peak cedar season (which will hit any day now), all it really does is keep us from being miserable, and at least functional. We rely on daily otc allergy meds to help out with the rest - but it takes a couple of days for them to be really effective. Zyrtec or claritin are our go-tos, and we have stacked benadryl on top of zyrtec for really bad days, though rarely, since I really don't like loading up on medicines, either. However, an anti-inflammatory can be helpful, too, since most of the pain issues are caused by swelling in the sinuses.
I hope at least some of this helps! Hang in there, mama.
