What do they look like?
- Dust mites (acarids), of the family of Arachnids (spiders) are invisible to the naked eye.
- They have four pairs of legs, and have hairs and claws on their tail end.
- They measure from 0.2 to 0.4 mm in length.
- They live only 2 to 3 months but reproduce very quickly when they find favourable conditions: humidity rate ranging between 65 and 80% and a temperature ranging between 20 and 30 degrees.
Where do we find them?
- There exist more than 50.000 varieties of acarids. Most often found in household dust the dermatophagoides pteronissimus (DPTER) and the dermatophagoides farinae (DF), are practically absent above 1800 meters.
- Dust mites develop indoors.
All houses, even the cleanest ones, host dust mites. They are found in bed linen, curtains, cuddly toys, settees, carpets, fitted carpets.
Some frightful figures
- They feed on human skin flakes, skin, hair and nail remains.
- One gram of dust can contain 2000 to 10.000 dust mites. Their presence does not mean that a home is badly kept.
- A mattress can contain 2 million dust mites.
- 4000 dust mites can be found under each footstep.
- They feed off the fifty million skin flakes that we shed during our sleep.
- They reproduce at a dizzying speed because a female lays 20 to 80 eggs which reach their adult stage at the end of 3 months.
- 0.25 grammes of skin flake can feed several million dust mites for 3 months.
- A rate of 2 mg of dust mites per gram of dust can sensitise an allergic person, and 10 mg per gram of dust cause an asthma attack.
Storage dust mites
We also find dust mites in barns, cattle sheds and warehouse attics. These storage dust mites, contrary to the domestic dust mites present in household dust, feed on flour, grain or cereal flakes.
- The acarus siro is found in the crust of certain cheeses.
- These dust mites cause the same types of symptoms as domestic dust mites.
Symptoms caused by an allergy to dust mites
- Dust mites are responsible for 50% of allergic symptoms.
- It is the remains of dead dust mites and their dejections which cause allergies.
- In a room with 85% humidity, dust mites eat 5 times more and produce 5 times more allergenic dejections.
- Their inhalation causes respiratory symptoms such as allergic rhinitis or asthma.
- Their contact with the skin causes a form of eczema still called atopic dermatitis.
- The symptoms caused by dust mites reach a peak in intensity in autumn and last throughout the winter because during these periods, the apartments are less ventilated and heated.
A person allergic to dust mites can develop allergic reactions eating shrimps or snails or by being in contact with cockroaches.
Advice to avoid dust mites
- Ventilate the bedroom every day, in winter as well as during the summer for 30 to 60 minutes each day.
- Change bed linen each week and wash them at the highest temperature.
- Get rid of fan heaters.
- Vacuum-clean two to three times a week.
- Wash at least once a month cushions, sleeping bags, covers at the highest temperature.
- Store clothing in a wall cupboard.
- Put cuddly toys one night per month in the freezer wrapped in a plastic bag.
- Maintain a temperature in the room from 18 to 19 degrees maximum and a moisture of 50 to 60%.
- Regularly remove dust from furniture with a wet cloth.
- Avoid bunk beds: the child sleeping in the lower bed inhales more dust mites coming from the higher bed.
- A slatted base is recommended in an allergic person's bedroom.
- Pillows and duvets should be made out of synthetic materials in order to avoid feathers where dust mites are likely to live.
- Use an anti dust mites cover , hermetic to dust mites, wrapping the mattress completely and advised by your doctor.
Vacuum-cleaning: a session must last 30 to 40 minutes to eliminate 20% of dust mites' allergens. The vacuum cleaner must have a HEPA filter, high effectiveness for air particles) in order to avoid blowing out the dust mites back into the air. Avoid fitted carpets, hangings, curtains...
Anti dust mite products
Be careful and do not invest too much money into anti dust mite products.
- Allergies and dust mites have become a real market for manufacturers.
- Thus, do not systematically trust "anti-dust mites" slogans which do not always offer a guarantee of effectiveness.
Vacuum-cleaning and Cleaning
- Dust 1 to 2 times a week with a wet cloth.
- Vacuum-clean surfaces covered with fitted carpets once or twice a week, in particular under the bed.
- The vacuum-cleaner should not reject the allergenic particles back into the room.
- The vacuum cleaner must be provided with a HEPA filter, with high effectiveness for allergenic particles, which reduces the amount of dust mites rejected into the room.
- The use of a double suction bag can be effective.
- Ventilate the bedroom after vacuum-cleaning.
- Brush and shake carpets outside the bedroom.
- Avoid vacuum cleaning sprays and detergents which can make allergic symptoms worse.
- Clean the tiling, parquet floor and pieces of furniture with a wet cloth or a mop.
Do not use a feather duster, because dust mites spread all over the room
The vacuum cleaner
There are several vacuum cleaners which meet these criteria.
Anti dust mite covers
The use of anti dust mite covers wrapping the mattress, pillows or duvets, decreases contact between the allergic person and dust mites.
These covers are machine-washable at 60 degrees.
Anti dust mite sprays
Anti dust mite sprays are chemical substances which kill dust mites. They must destroy dust mite eggs and larvae and some destroy also moulds which represent a source of important feeding for dust mites.
- Dust mites are found either in sprays, or as a powder, foam or liquid which is put in an appropriate spray.
- Many anti dust mite sprays are sold at chemists or directly by laboratories dealing with anti-allergic products.
One needs to be wary of certain products sold outside the medical sphere. They may have an impact on dust mites, but do not kill the eggs and larvae.
You can seek advice from your doctor or your chemist.
Never use an anti dust mite spray sold in a horticultural store and which is only used to treat plants.
Precautions when using anti dust mite products
- The application of the anti dust mite spray should not be made by an allergic or asthmatic person, as the product may cause an attack because of its irritating properties.
- Some sprays have a valve with an automatic release of the product in the bedroom.
- To treat all the favourite hiding places of dust mites, the mattress and seats made of cloth in particular.
- To treat both sides of mattresses.
- To leave the product to act for 2 to 4 hours, according to each brand.
- Ventilate the room for several hours.