One of the most important factors in the treatment of patients allergic to HDM is to reduce their exposure to HDM allergens. There is increasing evidence that avoidance measures against HDM allergens, such as reducing indoor humidity, the use of synthetic bedding encasings and the removal of carpets, can be effective. For example, a Dutch study compared the effect of different rug-cleaning methods (vacuuming, "wet cleaning", shampooing) or autoclaving on Der p I, Der p II and Der f II levels. The cleaning methods did not kill mites but significantly reduced allergen levels and destroyed mite habitat quality. Autoclaving killed mites and was the most effective method in both aspects, "Ventflex", a polyurethane coating, has been coated on to fabric to make occlusive covers for mattresses, pillows and duvets. Der p levels in mattress dust were all< 2ug/g in the Ventflex group (i. e. below the sensitizing level) and were 1%(100-fold reduction) of the levels in the control group, in which the bedding was washed and the mattress was vacuumed weekly.

Recent studies have tested the use of different types of chemicals, like natamycin, tannic acid, benzyl tannate complex and benzyl benzoate. These studies have had a mixed success. They usually produce a mild to moderate decrease in mite allergen concentrations in dust from carpets or mattresses, but the relationship with clinical improvement is often limited or absent.

It is not surprising that antifungal antibiotics such as natamycin do not reduce HDM levels; the reported association between fungi and HDMs has recently been re-evaluated and it has been shown that fungi exert both detrimental and positive effects. The application of selective fungicides may either increase or decrease HDM numbers. Fungi do not contribute directly to allergenicity and so fungicides are unlikely to lower allergen concentrations.

The use of occlusive covers in beds sprayed with a tannic acid/acaricide solution resulted in a nine told reduction in allergen levels for up to 4 weeks in one study, but the same treatment was only effective for up to 2 weeks in another study and did not result in any clinical improvement. Not only do these treatments produce short-lived effects, but contact sensitivity to tannin has been reported which would aggravate, rather thạn alleviate AD. When occlusive cover and tannic acid/acaricide solution treatment was combined with daily vacuuming of carpets, clinical benefits in patients with AD were observed suggesting that further measures are required to prevent house dust mite reinfestation.

Several control attempts have been made against HDM using the acaricide benzyl benzoate, which has been widely used to kill scabies mites for over 100 years. These different trials, performed in various countries, have given conflicting results. Furthermore, a suffocating odor has been reported following treatment with benzyl benzoate.

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