House Dust Mite Allergy

Why does the house dust mite cause allergy symptoms?

In people allergic to dust mite, it is often not the mite itself but proteins in their droppings which cause the allergy symptoms. Each mite produces about 20 of these waste droppings every day and they continue to cause allergic symptoms even after the mite has died.

What are the common symptoms of a house dust mite allergy?

House dust mite allergy is very common and is associated with triggering or worsening symptoms of asthma, eczema, and perennial or chronic allergic rhinitis.

The most common symptoms of a house dust mite allergy include sneezing, runny nose, stuffy nose, itchy nose, throat or mouth, postnasal drip, cough, red or watery eyes, fatigue, itchy or worsening eczema or asthma symptoms. Often symptoms can affect you all year round (this is called chronic) and so you may not realise you are allergic to house dust mites in your environment and have just put up with your symptoms.

Symptoms can become worse after sleeping in a heavily- infested bed, after changing bedding, doing housework or when sleeping in an old house, particularly if damp; but can simply be chronic when exposure is regular. Treatment includes reducing exposure to house dust mite through reduction/ eradication techniques.

How can I treat my symptoms?

Treatment for allergic rhinitis triggered by house dust mite allergy often include nasal douching, non- sedating antihistamines, intra nasal antihistamine preparations, with the addition of Inhaled corticosteroids or combined inhaled corticosteroids and antihistamine sprays depending on the severity of the symptoms.

If despite using these treatments, your symptoms are still troublesome, then it is worth speaking to your healthcare professional as other treatments are available. If your symptoms are severe then you may be referred onto a specialist for further assessment.

Desensitisation (immunotherapy) to house dust mite allergens is a possible treatment for those severely affected. This involves giving gradually increasing doses of the allergen under supervised conditions so that you no longer have severe symptoms when exposed to the allergen.

How can I reduce my exposure to house dust mites?

A significant amount of exposure to house dust mite allergen happens in the bed, so taking precautions in the bedroom by using allergy friendly covers on bedding, including on all pillows, is a first step. Washing bedding regularly can sometimes help, although clinical trials suggest that multiple measures need to be taken, possibly including the use of chemicals called acaricides, in order to see an effect. However, remember that dust mite allergen is found in all rooms of the house, on the floor and in soft furnishings, not just in the bedroom and are also present for example in the workplace and cars.

Measures to avoid house dust mite will lower, but do not totally remove, dust mite allergens. Often, this will be sufficient to significantly improve symptoms, but sometimes, the reduction may simply not be enough to result in a noticeable difference. There is no way to predict whether someone will benefit from avoidance measures, except by trying them. Remember that it is better to carry out several allergen avoidance measures properly in order to see an improvement in symptoms. Just doing one or two things may not make any difference.

Controlling house dust mite allergens

At home:

Most efforts at controlling dust mites should be aimed at areas of the home where you spend most of your time and where dust mite load is greatest, i.e., bedrooms and living areas.

• Use allergen-proof barrier covers on all mattresses, duvets, and pillows. These should be breathable and should completely enclose the item. Buy products that have been tested to make sure that they prevent the escape of house dust mite allergen.
• Wash all bedding that is not encased in barrier covers (e.g., sheets, blankets) every week. Washing at 60 degrees centigrade or above will kill mites. House dust mite allergen dissolves in water so washing at lower temperatures will wash the allergen away temporarily, but the mites will survive and produce more allergen after a while.
• Allergic children should not sleep in the bottom bunk bed where allergen can fall onto them.
• If possible, remove all carpeting in the bedroom. Vacuum hard floors regularly with a high-filtration vacuum cleaner (see below).
• Remove all carpeting from concrete floors. Such floors trap moisture allowing dust mites and mould spores to thrive. Seal the floor with a vapour barrier, and then cover it with a washable surface such as vinyl or linoleum.
• There are certain types of flooring designed to prevent allergen build up (details of suitable floorings are available from Allergy UK).
• Where carpets cannot be removed, vacuum regularly with a high filtration vacuum cleaner. Use a high-temperature steam-cleaner to kill mites effectively. Products are available that can be sprayed on carpets to kill mites; these are effective but should be used with care if you suffer from respiratory symptoms and should not be used in areas where children play on the carpet, or on soft toys or pillows.
• Use a high-filtration vacuum cleaner with filters capable of retaining a high proportion of the smallest particles (HEPA filter, S-class filter or similar). Details of suitable vacuum cleaners are available from Allergy UK.
• Damp-wipe all surfaces each week (pelmet tops, windowsills, tops of cupboards and so forth).
• Use light washable cotton curtains and wash them frequently. Reduce unnecessary soft furnishings.
• Vacuum all surfaces of upholstered furniture at least twice a week.
• Washable stuffed toys should be washed as frequently and at the same temperature as bedding. Alternatively, if the toy cannot be washed at 60 degrees place it in a plastic bag in the freezer for at least 12 hours once a month and then wash at the recommended temperature.
• Reduce humidity by increasing ventilation. Use trickle-vents in double-glazing, or open windows. Use extract fans in bathrooms and kitchens.
• If necessary, use a dehumidifier to keep indoor humidity under 50% (but over 30%)

In your car:

House dust mites can live in the soft furnishings and vents of motor vehicles, so similar cleaning measures inside these is also important.

At work:

• Ventilation is extremely important. Whether it is windows, trickle vents or an air conditioning system. Ensure that you have clean air in and around you in the workplace.
• If you have a heating, ventilation, and air conditioning (HVAC) unit installed, make sure it is regularly serviced.
• If ventilation is limited, use an effective air purifier to help remove and reduce allergens such as pollen, house dust mite debris and mould spores.
• Review flooring and furnishings.
• Ensure office cleaners have effective cleaning methods and equipment.