House dust mite allergy

Reviewed by Dr Paul Klenerman, specialist and Professor Brian Lipworth, professor of allergies and respiratory medicine

What is house dust mite allergy?

House mite allergy is a hypersensitive reaction to proteins in the excretion of dust mites. The protein attacks the respiratory passages causing hay fever and asthma. It will aggravate atopic dermatitis in people who have a tendency to this problem.

House dust mites are found in all homes. They are microscopic organisms that thrive in warm and humid houses with lots of food - human skin. The mites prefer to live in beds and, because we spend about a third of the day in bed, we inhale large quantities of dust mite allergens.

How do you become allergic to house dust mites?

The excretion of the mites contains a number of protein substances. When these are inhaled or touch the skin, the body produces antibodies. These antibodies cause the release of a chemical called histamine that leads to swelling and irritation of the upper respiratory passages - typical asthma and hay fever symptoms. The predisposition for allergy is often hereditary.

Unlike pollen, dust mites are present all year round causing constant allergy - 'perennial' allergic rhinitis. The excretion from the mites dries out and can be launched into the air when someone walks over a rug, sits down in a chair, or shakes the bed clothes, giving allergic people immediate symptoms.

What are the symptoms of house dust mite allergy?

Hay fever, runny nose, itching, sneezing.

Watering eyes.

Asthma, difficulty in breathing.

Infantile eczema (a skin disease) may get worse.

What makes the symptoms worse?

Air pollution such as tobacco smoke or car fumes.

How does the doctor make the diagnosis?

It is often enough to tell the doctor when, where and how you get the symptoms. Skin tests and various blood tests can be used for confirmation.

Good advice

It is best to do everything possible to avoid hypersensitivity to house dust mites. People who have perennial rhinitis, inflamed mucous membrane of the nose, or are allergic to house dust mites should try to adapt their homes.

Have as little furniture as possible in which mites can live.

Clean walls, woodwork and floors with wet cloths. The floor can be polished.

Only use rugs that can be washed once a week.

Use bedding that can be washed often, cotton sheets, washable bottom sheets and synthetic blankets or duvets. Don't use woollen blankets or quilts.

Make sure your chairs are made of wood or plastic.

If you can, use plastic curtains and dust them daily.

Use wet cloths and a vacuum cleaner with a no bag vortex and allergen filter to clean the house thoroughly, preferably every day, but at least twice a week.

Avoid dust traps like teddy bears, cushions, dried flowers, bric-a-brac and toys.

Wash bedding etc at a temperature of at least 60°C to kill the house dust mites.

Leave bedding, duvets, pillows and mattress hanging outside for an hour every day or as often as practical.

Put duvets and pillows in plastic bags and put them in the freezer for 24 hours at least once a month.

You may want to sleep on a cheap mattress that you can exchange for a new one at least every six months.

Dust mites hate dry and cold air, so try to air the house every day and don't use an air humidifier, which will only make matters worse. If the lower edge of the window is moist when you wake up in the morning, there is too much humidity in the air.

Do not spray the house, it may worsen your symptoms.

Do not touch dusty objects like books and old clothes.

When you are likely to be exposed to substances that give you a reaction, eg when you are house cleaning, you should wear a mask.

Don't allow smoking in the house.

What complications are possible?

You are predisposed to other respiratory diseases.

You are also predisposed to otitis, inflammation of the ear.

You may have trouble sleeping and suffer from chronic fatigue.

Hospitalisation following a severe asthma attack.

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