The only intervention that has proven to be useful for management of allergic conditions like Asthma & Eczema, in people allergic to House Dust Mite is Anti DUST MITE protectors. Special vaccum clenaers, special bedding etc. do not help.
You need to vaccum the carpet well, control humidity and wash the bedding and soft toys at 60 C to kill the mite.You don’t need to buy the whole mattress, pillow or duvet. Just cover them with these special protectors and they might help.