Dust Mites and Diseases

Dust Mites are a big worry for allergy sufferers so today we have have invited Nell Nockles from Housedustmite.com to fill us in with some fascinating facts on Dust mites. For more information on dust mites and allergies visit www.housedustmite.com.

Humans have always been exposed to dust mites, but the level of
exposure in ‘western’ living now needs review because mites have
become a problem. To tackle house dust mite infestation and
related disease, doctors say it is essential to understand mite
biology, where they live and why they cause allergy. To help you
here are ten facts in each of these three categories ending with
advice on how to kill mites.

Biology

House dust mites are tiny scavengers that eat organic débris including
discarded skin scales covered in bacteria, fungi and yeasts.
They live for about three months in colonies that have damp, warm, still
environments. Adult mites are small enough to sit on the tip of a pin.
House dust mites are up to 75% water in weight, and must maintain this
water in order to breed. They grow best at 25°C (77°F) in 65-75%
relative humidity (RH). Below 50% RH a mite will not function.
Six stages of a mite’s life are; egg, pre-larva, larva, two 8-legged nymph
stages and finally an adult. A healthy female can produce up to 60 eggs
in her lifetime.
Dust mites are blind, take in water and oxygen through their shell-like
covering, and can produce up to 20 droppings a day. Like rabbits,Dust mites
consider their droppings as a source of food.
They have no ‘stomach’ but a chambered gut that contains powerful
digestive enzymes designed to break down scraps of food. Both leftover
food and enzymes can be found in mite droppings.House dust mites eat a special fungus that survives its toxic gut and
then grows again out of the Dust mite’s dropping. Doctors think the fungus
survives because it may be helpful to the Dust mite’s survival.
Adult Dust mites travel about using suckers and hooks on each leg and
navigate using their exquisite sense of smell, and by paying attention to
signalling vibrations from other mites.
Scientists think mites eat rotting skin scales because the contents in the
skin help make a ‘perfume’ to attract a mate, a necessary aid for a blind
animal.
Researchers took 4 mites and let them breed in the best conditions for
four months, when they finally looked they had over 1200 mites.

Where they live

House dust mites evolved about 23 million years ago as nest dwellers, living in colonies scavenging on organic matter. Rats and birds nests
were common homes for an ancient mite colony.
Modern man has become an indoor species and in so doing has invited
mites to come and live in his warm, humid, cluttered ‘nest’ or home.
At best, mites can travel 2 centimetres a minute, but if attached to cloth
they can travel the globe.
One hundred years ago man’s battle was with storage mites that spoiled
grain stores, now it’s the turn of the house dust mite that can threaten
human health on a global scale. Both storage mites and house dust
mites can cause allergy.
Both mite species (storage and house) can live indoors in barns, homes
and sheds living in items such as grains, hay, clothing, carpets or
mattresses.
In an old mattress a researcher found both dead and alive mites, mould,
fungi, pollens, bacteria, and discarded rotting skin scales – all mite food!
By covering a mattress with micro-porous material, mites are too big to
enter the mattress, but if left alone they can colonise on the top of the
covers in old dust. Micro-porous covers should be damp dusted
frequently to prevent mite colonization.
A clinical study took a colony of house dust mites, coloured them red
and let them go in a home. Later one was found in the family car – most
travelling mites don’t survive to establish a colony.
When on the look out for dust mite nest sites, don’t forget the blanket in
a pet’s basket. Dogs and cats can also suffer allergy to mites.
Control mites by reducing indoor humidity to less than 51% relative
humidity (RH). Below 51% RH is considered hostile to mites but
comfortable for man. Below 40% RH can be ‘too dry’ for human comfort.
Watch for nest sites that have their own microclimates, such as beds.

Allergenicity

Allergens from dust mites can come from their body parts, saliva, or their
droppings. Mite-related diseases include allergic asthma, rhinitis
(hayfever), conjunctivitis, sinusitis, atopic dermatitis (eczema), or any
combination of these.Check with your doctor for further details.
Three different species of house dust mites and three species of storage
mites cause most of the allergy problems worldwide.
Storage mites and house dust mites are different animals with similar but
different allergens. If you’re allergic to mites, make sure you know which
one to avoid.
 Dust mite droppings are wrapped in a film that dissolves on contact with
moisture. Once dissolved, they release their contents of active enzymes,
scraps of food, and fungi.
Of the 22 known allergens from dust mites, seven are active digestive
enzymes and several are classified as unknown.
One of the major allergens (Der p1) is an enzyme similar to a product
used in the food industry to tenderize meat.
It is this enzyme that enters the body by melting the ‘glue’ that binds
delicate cells together. For most people a ‘repair’ is quick, but for those allergic to mites a reaction can occur.

There are five simple ways to kill dust mites

1) hot washing laundry and carpet & upholstery cleaning 2) freezing, 3) exclusion 4) poisoning, 5) dry them out by reducing humidity or putting clothes or soft toys in a tumble drier
for 10-15 minutes. Drying is best because house dust mites are up
to 75% water in weight and need to keep this level in order to
breed. A dead mite will leave behind allergens that should be
destroyed or avoided to protect the vulnerable.
To stop dust mite larvae and mite droppings (allergens) from passing
through fabric, cloth pore size should be woven to less than 10
microns.

Neil Nockles

visit www.housedustmite.com to learn more about dust mite.

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