Allergy Awareness Association
Heres what the Allergy Awareness Association have to say:
“Irritated watery eyes, runny and stuffy noses, sinuses, skin problems, respiratory
difficulties and asthma can often be due to an undiagnosed allergy, many of
which can be caused by house dust mites and mould. Some estimates have
up to 30% of all people being allergic to house dust mites. In a warm, damp
environment, you have an atmosphere in which dust mites thrive. Dust mites live in our furnishings,
bedding, carpets and clothing and can cause havoc if you have an allergy. Allergy Awareness Association
recommends a good dehumidifier be used to assist in reducing humidity levels in our homes.”
We know there is a link between Allergy/Asthma and Dust Mite activity. This is a real
problem in many NZ homes as the following statistics show:
- 1.2 million new Zealanders suffer from allergy.
- NZ has one of the highest rates of allergy to house dust mite and cats in the world.
- Allergy to the house dust mite causes Asthma, hayfever, allergic rhinitis,
allergic conjunctivitis, eczema, and glue ear.
- More than 200,000 NZ children have eczema.
The following is adapted from Auckland paediatrician Dr Allen Liangs' address
at Allergy Awareness Associations AGM in 1999 - courtesy Allergy Awareness
Association. Allergy Awareness Association recommend a good dehumidifier be
used in helping to control dust mites in our homes - here is why!
- House dust mites are ubiquitous eight legged creatures that are part of the
Arachnid family. Dust mites are not insects, but are relatives of spiders,
chiggers and ticks. The mites that commonly cause allergies are of the Pynoglyphoid
genera, especially the species Dermatophygoides pleronyssinus, Dermatophygoides
farinae and Blomia impacalis.
In NZ and Australia, the most prevalent species are the Dermatophygoides pleronyssinus
and its near relative D.farinae. Scientists use Latin names to describe how the mites
can be bred under laboratory conditions - Dermato means skin, or dander of animals,
including human skin. Phagoides means to eat or to consume. Pleronyssisis comes from
the same root as the word pterodactyl (the dinosaur with feathers) and means feather,
while farinae means flower. So the house dust mites in our homes love and thrive on
human and other animal skin droppings, and flour which can be found in biscuit and
breadcrumbs. In fact, these mites also love a nice serving of mould as part of their
diet as well.
As dust mites are totally blind, they have evolved a system to decide whether particles
they have just come across are food or waste that they have already extracted all nutrients
from. After they have ingested a parcel of skin dander, they envelop it with a wrapping of
their own digestive proteins. These enzymes extract all the nutrients they need before
discarding the wrapped package as facal pellets.
If the mites then come across these pellets later, they can recognise the chemical signature
of mite droppings and avoid ingesting them again. Unfortunately, allergic people can be
sensitive and react badly to the enzymic proteins in these facal pellet wrappers.
The pellets are about the same size as our red blood cells and shaped like a collapsed
muffin. They are relatively heavy for an allergenic particle, and when disturbed can
stay in still air for around half an hour (compared with cat allergens, which can stay
suspended for up to 75 days!). Exposure to the dust mite is more intense for children
and adults in a horizontal position on our mattresses because of proximity to the
source of dust mite facal pellets.
Old mattresses easily carry up to a million dust mites. Given enough food supply,
each mite can process and package four facal pellets per day. With four million
allergenic particles disturbed when people engage in bed activities, it is no wonder
there is not only shortness of breath, but also wheezing and hard breathing associated
with such activities! It pays to keep our mattresses clean!
House dust mites cannot drink. They obtain water partly from their food but the bulk
of water needed is obtained by a mechanism of hygrophilic (water loving) crystal in
their armpits. These finely structured crystals can obtain enough water for the mite
when the relative humidity in the air is above 60%. The mite must tone down its
activity if the relative humidity drops below this figure.
In Auckland, the relative humidity is above 80% year round, which explains the very
high levels of dust mite counts in this city environment. The hygrophilic crystals
also protect the dust mite from dehydration when conditions are dry. Crystals can be
damaged (by being frozen). Such damage increase the rate of defaccation which can
hasten the death of the dust mite when exposed to sunlight. Persistent heat above 60
degrees C also kills the mite and its eggs.
For children who are genetically prone to developing allergies, exposure to dust
mite allergens is likely to result in dust mite allergy. The chances of allergy
development depends not only on the degree of exposure, but also the timing as well.
It appears that exposure during the first six months of life is most likely to initiate
the allergy. Continued exposure and dose of exposure can result in allergy diseases.
Data from the ETAC study of children with chronic eczema indicated that confirmation of
house dust mite allergy from skin prick testing is dependant on the maturation of the
skin, with less than 1% positive skin reaction at age one, and 13% at age five.
The study also confirmed previous finding of the relationship between having wall to
wall carpeting and the development of this allergy. For example in Spain where the
climate is usually warm and moist, there is almost universal association between
hose dust mite allergy and carpeting in those genetically prone. In England where
95% of homes studied have wall to wall carpets, about one third of the children
studied have confirmed dust mite allergy. However, in Scandinavia very few households
have carpet and almost none of the children studied have mite allergy.
Therefore, control of house dust mites consists of the following:
- Reduce their food supply. Have a bath or shower before going to bed. Do
not eat on the bed or on soft furnishing where house dust mites abound. Do not
keep animals in bedrooms.
- Reduce dust mites from their reservoirs. Using dust mite covers. These are
a very efficient way of keeping the dust mite inside mattresses and stopping the
food supply from entering into mire colonies. Plastic sheets are good only when
they are brand new.
- Remove wall to wall carpeting. Fixed carpets, especially those with thick
underlay, provide excellent protection for the dust mites. Even the strongest
vacuum cleaner cannot produce enough draught in the depth of the carpet piles
to dislodge them. Rugs are the best way to go.
- Vacuum cleaners are efficient in removing easily dislodged particles. Be
sure to have a fine enough exhaust filter, otherwise particles will just be
redistributed through the room.
- Soft toys should be frozen in the freezer (this breaks down the hygrophilic
crystals in the dust mites armpits) and then followed by sunning for six hours
or more every two to three months.
- Boiling or heating to above 60 degrees C is efficient in killing the mites,
as is prolonged sunning. Insecticide sprays turn out to be efficient only very
temporarily and all marketed products also affect other insects that are predators
or competitors of the mite. As the mite eggs survive and hatch, there is no
longer adequate competition to hold their numbers down and the population may
even expand.
|
Feedback
