House dust mites can trigger allergic reactions such as asthma, eczema and rhinitis (runny nose). Cutting down mite numbers may reduce these reactions. The information below aims to give advice on how to reduce mite numbers in the home.
What are house dust mites?
House dust mites are creatures so small they cannot be seen with the naked eye. They live in our homes and feed mainly on the scales of the skin that we shed. They are most common in warm, damp, dark areas where dust containing skin scales gathers. These areas include pillows, mattresses, carpets, soft furnishings, soft toys and even clothing.
The mites are harmless to most of us, but they can cause allergic symptoms in some people. These symptoms are caused by breathing in substances known as allergens which are in the mites' droppings. The droppings are tiny, dry pellets which forms a large part of the dust in areas where mites are found. The pellets are so small that they can become airborne, and may then be breathed in.
Other allergens which can trigger allergic reactions include moulds, cats and dogs, or pollen from trees and grasses.
Why do they need to be controlled?
In this country, about two and a half million adults suffer from asthma and one child in seven is affected. House dust mite allergen is one of the most common triggers of asthma. About one in ten of us has a family tendency to develop allergic asthma if we are regularly exposed to high levels of allergens - controlling the levels of allergen could stop prevent this, and is particularly important for very young children.
If you have allergic asthma it is quite likely that you are allergic to house dust mites. If you think that you or your family may be allergic to house dust mites try taking the first steps below to see whether there is any improvement - if you are in doubt you should consult your doctor.
You cannot get rid of all the mites from your home - but you can reduce the numbers.
For best results, carry out the steps all over the house, but especially bedrooms, which are likely to be where most time is spent.
It can take at least two months before the effects can be noticed - carry out steps one and two, then see if allergic symptoms improve.
Step one - reduce the dampness in your home
House dust mites prefer warm, damp homes. Dampness leads to the growth of moulds, which can cause allergic reactions. Follow these tips to avoid dampness:
- Open windows or vents in kitchens and bathrooms - during and after cooking, washing and bathing. Stop dampness spreading, and keep these doors closed
- Avoid drying clothes indoors (especially in bedrooms and living rooms) unless using driers which are vented outdoors
- If you have to dry clothes indoors, open a window and close the door to the room
- Leave the bed open to air before remaking it
- Open windows or vents in bedrooms
Step two - prevent the build up of dust
Removing dust is important in the homes of allergy sufferers - to help prevent dust building up try the following.
- Reduce the number of items on which the dust can build-up, especially if they are difficult to clean. Store ornaments in display cabinets, books in closed cases, and clothes and other objects in cupboards or drawers
- Regularly clean surfaces and objects where dust collects using a damp cloth
- Regularly wipe down window blinds with a damp cloth
- Vacuum clean soft furnishings and curtains as well as carpets and floors
- Replace the air filter or dust bag in the vacuum cleaner regularly
- Vacuum clean mattresses every two weeks
Step three - high temperature washing
Washing fabrics at a minimum of 60oC kills dust mites - so buy sheets, pillow cases and duvet covers that can be washed at high temperatures, and wash them at least every two weeks. Also get curtains that can be washed at 60oC and wash regularly.
Step four - bedding and soft toys
House dust mites are found in large numbers of mattresses and pillows where there are lots of skin scales. To reduce the number of mites in these areas:
- regularly wash pillows at 60oC or replace with new ones every six months
- replace blankets with duvets which are made of synthetic material
- cover all mattresses, duvets and pillows in the sufferer's bedroom with micro-porous membrane covers- they need to be wiped clean with a damp cloth each time the bedding is changed
- Stuffed toys can also contain house dust mites so try to reduce the allergy sufferer's contact with these toys. Keep the toys away from the bed if possible.
- about once a month put soft toys in the freezer for 6 hours to kill the house dust mites, then wash to remove the remaining allergen
Step five - carpets
Carpets also contain a lot of house dust mites. Replacing carpets can be expensive but if you are going to change your carpet anyway these options will reduce the number of mites present:
- Replace carpets with linoleum, vinyl flooring or sealed natural flooring such as cork tiles or wood - ensure that the new floor does not have cracks which enable dust to build up
- Choose very short pile synthetic carpets as they tend to hold fewer mites than long piled wool carpets
- Use cotton rugs that can be washed at high temperatures and wash them regularly
Step six - high efficiency filter vacuum cleaners
There are vacuum cleaners on the market which are better at collecting dust than ordinary vacuums, so consider buying a high efficiency filtered vacuum cleaner and use regularly on floors, carpets, soft toys and soft furnishings.
Step seven - treatment of furnishings
Every three to six months treat carpets and soft furnishings with either of the following to kill mites:
- Acaricides/antigen denaturing compounds - for your own health and safety it is very important that you follow the instructions for use and disposal
- Liquid nitrogen, which should only be applied by a specialist contractor
Step eight - replace furnishings
When you buy new furnishings you should consider replacing woven-fabric covered chairs and sofas with cane, canvas, leather-like or leather-covered furnishings which are easy to clean and do not harbour house dust mites.
Other possible measures
Products such as air filters, ionisers, dehumidifiers and mechanical devices for ventilation with heat recovery are available. These may also help to reduce allergic symptoms, but their effectiveness has not yet been fully tested.