The causes and triggers of allergies are nearly all found in our daily environment. And exposure to high concentrations of house dust allergens at a very early age greatly increases the risk of suffering from diseases such as asthma later on.

The house dust mite and its excrement are one of the most widespread causes of allergies. Our houses are becoming ever more modern and home comfort standards are rising; good insulation ensures constant room temperature and rather high relative humidity. But these conditions, which are very pleasant to us, are also excellent prerequisites for the propagation of house dust mites.

Allergen-containing mite excrement on fibers:  Initially held together by a layer of slime, the fecal matter gradually falls apart into very tiny particles. The allergenic dust then flies up into the surrounding air and is inevitably inhaled as we breathe.

Invisible culprits - mites and mold

House dust mites and mold fungi are found in every household. Even with regular and thorough housecleaning, dust particles and human skin scales continuously accumulate. Mites derive their principal nourishment from these human and animal skin scales, but also feed on fungal mold.

Mold fungi are a further allergy trigger and form a mutually beneficial partnership with mites. Fungi split up keratinous skin scales, and the resulting cleavage products provide nourishment for house dust mites. In this way mold fungi serve not only as direct nourishment for mites but also as "pre-digesters". These microbial metabolic products also lead to unpleasant odors and mildew stains.

It is not the mites themselves that contain allergens but their excrement - triggers for asthma, eczema and allergic nasal mucous membrane inflammations.

The house dust mite has a life span of about four months. During this time it produces about 200 times its weight in excrement and lays up to 300 eggs. This makes it clear why the concentration of allergens in a room increases exponentially within a very short time.

Warmth and humidity promote mould fungi.  The Aspergillus shown here (enlarged lOOOx) is capable of causing lung diseases.  Millions of its spores (seeds) in the surrounding air get into our lungs as we breathe.

Mattresses are particularly liable to be infected by house dust mites and mould fungi. This is not surprising when we realize that during eight hours of sleep the human body gives off perspiration, fat and skin scales.

Remedial Action

• Keep equipment water reservoirs clean and potable water systems adequately chlorinated, according to manufacturer instructions. Be sure there is no standing water in air conditioners.

• Repair leaks and seepage. Thoroughly clean and dry water-damaged carpets and building materials within 24 hours of damage, or consider removal and replacement.

• Keep relative humidity below 50 percent. Use exhaust fans in bathrooms and kitchens, and vent clothes dryers to outside.

• Control exposure to pets.

• Vacuum carpets and upholstered furniture regularly. Note: While it is important to keep an area as dust-free as possible, cleaning activities often re-suspend fine particles during and immediately after the activity. Sensitive individuals should be cautioned to avoid such exposure, and have others perform the vacuuming.

• Preferably a commercially available HEPA (High Efficiency Particulate Air) filtered vacuum should be used.

• Cover mattresses. Wash bedding and soft toys frequently in water at a temperature above 130^oF to kill dust mites.