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The house dust mite
Dermatophagoides pteronyssinus is about half the size of a dot
or period on a newspaper. The mite has no eyes, no organised
breathing system, cannot drink and lives for approximately 3-4
months. Twenty droppings a day may be produced by the mite,
which means approximately 2000 during its lifetime. The HDM can
get nourishment from its own droppings and may eat them up to
three times over. The females can lay from 60-100 eggs depending
upon living conditions, which ideally, are warm dark and damp
for breeding mites. Most modern conventional beds provide
perfect breeding conditions!
The mite will not bite. It is a scavenger with a preference for
discarded old mouldy human skin scales. As a scavenger, however,
it will eat pollen grains, insect scales, house dust, plant
fibres and old bits of dead mites. The mite is a necessary
cleaner in nature. We must learn to understand and respect the
house dust mite. This simple creature has been on earth for
about 23 million years. It has lived with man for about 10,000
The most important thing to know about the mite is that it
consists of up to 80% water. A tiny bag of water! Without water
it will not thrive!
How do they affect me?
One of the major results of sensitivity to mites for certain
genetically predisposed individuals is an allergic reaction .
Allergic asthma, rhinitis ( hay fever) and some types of eczema
can be the result of this sensitivity. Up to 85% of asthmatics
are allergic to the mite in the UK and it is recognised as a
major cause of allergy world-wide.
Mite droppings are a main source of the problem. Dung pellets,
if disturbed by activity, are pushed into the air. If this
happens in an unventilated room, they can remain suspended in
the still air to be breathed in by unsuspecting people. An
invisible soup of dirt! It takes approximately for 20 minutes
for this 'dust' to settle. Powerful enzymes in the droppings
that are designed to break down scraps of food may also break
down the protective lining of the lungs, nasal passages or
lining of the eyes. This will only happen to certain sensitive
people described by doctors as atopic.
Reduce the humidity in your home. The mites will not thrive
below 64% relative humidity.
Air all beds and bedding all day. Don't make your bed in the
Regularly wash all bedding on a hot wash (+60°C).
If possible have two duvets. These can be difficult to clean and
dependant upon weather for drying. One duvet should be clean and
ready to put on the bed.
Cover conventional mattresses and pillows with micro-porous
material to prevent infestation. Make sure you damp-dust these
Open a window after a shower or bath or while cooking (if
possible) to let steam out.
Use a vacuum cleaner with high filtration features. If your
vacuum cleaner is not a high filtration variety, never reuse
Always open windows (if possible) when cleaning. Any disturbed
allergens will be blown outside on a draught of air.
On sunny dry days, air your home and hang out rugs or blankets.
Mites hate sunlight and will try to hide!
Mites cannot control their body heat. Therefore a visit by soft
toys or other small items to the freezer or tumble drier (hot)
will devastate a mite colony. However, a hot wash followed by
thorough drying is really the best way to prevent mite colonies
from becoming established.
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House mould allergies have been linked to a number of health
concerns, including asthma, fatigue and chronic cough. Moulds can
be found almost anywhere, although they prefer dark, humid and
warm locations. Bathroom condensation, leaky areas of the roof,
plumbing leaks and water seepage in basements can all attract
mould. You may also discover mould in some of the following, less
closets (where the mould may be transferred to clothing or
Symptoms of a mould allergy vary. In addition to those mentioned
above, you might experience wheezing, skin rashes, nasal
congestion, a sore throat, itchy eyes and shortness of breath.
The best way to avoid moulds is to take pre-emptive action. Keep
plumbing in good repair, and try to maintain and indoor humidity
of between thirty and forty percent. Remove items that have been
contaminated by moulds, including carpet, if necessary.
Someone who doesn’t react to the allergen should clean areas
with mould, preferably with detergent. If you have to clean the
area yourself, wear gloves and a protective mask. After
showering, wipe the shower clean to hinder mould growth. If you
have a fan in the bathroom, use it while showering or bathing to
Toxic Mould Allergy
Toxic mould produces substances called mycotoxins, chemicals that
can cause seizures, skin rashes, respiratory difficulties,
fatigue, coughing up blood, and even death. Toxic mould can harm
anyone's health, but is especially dangerous for people with
If you suspect toxic mould has entered your house or workplace,
talk to your allergist. Have your house inspected for the deadly
intruder. In extreme cases, toxic mould has spread throughout
buildings so thoroughly that the buildings have had to be
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Cockroaches and Allergies
The cockroach is an unwelcome guest anywhere. If you needed
another reason to dislike the pests, consider this: between 17
to 41 percent of Americans are allergic to cockroach allergens.
People react to the faeces of the cockroach, which can easily
become airborne. The cockroach actually shares an allergen,
tropomyosin, with dust mites.
Cockroaches prefer dark areas with plentiful food and water. For
that reason, they can often be found lurking in kitchens,
bathrooms, and often inside walls. They also favour areas behind
dishwashers, refrigerators and water heaters. They reproduce
prolifically, so elimination of the little beasts is a problem
best left to professional exterminators. In order to keep your
house roach-free, consider taking some of the following
Seal all cracks in walls to prevent entry.
Wash dishes promptly, and clean up any spilled food immediately.
Store food in airtight containers.
Seal garbage containers.
Keep plumbing in good repair.
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Your pet's dead skin
flakes, urine, faeces, saliva and hair can trigger asthma. Dogs,
cats, rodents (including hamsters and guinea pigs) and other
mammals all can trigger asthma in individuals with an allergic
reaction to animal dander.
Proteins in the dander, urine, or saliva of warm-blooded animals
(e.g., cats, dogs, mice, rats, gerbils, birds, etc.) have been
reported to sensitize individuals and can cause allergic
reactions or trigger asthma episodes in individuals sensitive to
animal allergens. The most effective method to control animal
allergens in the home is to not allow an animal in the home.
If you remove an animal from the home, it is important to clean
the home (including floors and walls, but especially carpets and
upholstered furniture) thoroughly. Pet allergen levels are
reported to stay in the home for several months after the pet is
removed even with cleaning.
Isolation methods to reduce animal allergen in the home have
also been suggested by reputable health authorities (e.g.,
keeping the animal in only one area of the home, keeping the
animal outside, or ensuring the allergic or asthmatic individual
stay away from the animal) but the effectiveness of these
methods have not been determined. To the contrary, several
reports in the literature indicate that animal allergen is
carried in the air and by residents of the home on their
clothing to all parts of the home, even when the animal is
isolated. In fact, animal allergen is often detected in
locations where no animals were housed. In these situations, it
is assumed that the allergen was carried in on people that have
animals or on people that have been around animals or people
Often people sensitive to animal allergens are advised to wash
their pets regularly. Recent research indicates that washing
pets may only provide temporary reductions in allergen levels.
There is no evidence that this short term reduction is effective
in reducing symptoms and it has been suggested that during the
washing of the animal the sensitive individual may be initially
exposed to higher levels of allergen.
Thus the most effective method to control exposure to animal
allergens is to keep your home pet free. However, some
individuals may find isolation measures to be sufficiently
effective. Isolation measures that have been suggested include
keeping pets out of sleeping areas, keeping pets away from
upholstered furniture, carpets, and stuffed toys, keeping the
pet outdoors as much as possible, and isolating sensitive
individuals from the pet as much as possible.
Children who are exposed to
animals from birth are less likely to develop allergic reactions
to animals later in life. Be cautious when introducing new pets
into a household suffering from allergies.
An important note on birds and
Be very cautious if you have young children and
babies and you keep birds or reptiles. Birds carry diseases that
can be transferred to humans and baby's are particularly
There is now conclusive evidence
that reptiles (snakes, lizards, tortoises, frogs etc) infect
children with salmonella. This extract below from the
NARMS Scientific Meeting held March
15-16, 2001, in Rockville, MD
one of the most common causes of bacterial diarrhoea in the
United States . The total number of Salmonella infections
over a 10-year period was reported at 441,863 people, mostly in
infants . The major source of Salmonella infection is food.
However, an estimated 3 to 5% of all cases of Salmonellosis are
associated with exposure to exotic pets.
Since the early 1970s small turtles (shell measured less than 4
inches) were banned, from sale in pet stores because one-quarter
million infants and small children younger than 5 years of age
were diagnosed with turtle-associated Salmonellosis . This
FDA regulatory action, which is still in effect, reduced the
number of Salmonella cases by 100,000 in children 1 to 9 years
of age [2,8]. However, in recent years the incidence has been
increasing. Currently, approximately 1.4 million Salmonella
illnesses occur each year, resulting in 600 deaths annually in
the United States . Salmonella serotype marina is becoming
increasingly prevalent, especially among infants and children in
households where pet iguanas and other reptiles are present. One
recent study reported in the United States, showed Salmonella
serotype marina infecting 81% of infants. Thirty-four percent of
these children were hospitalized, but only 14% had touched the
household reptile directly . In 1993, a rise in
reptile-associated Salmonellosis was associated with an
estimated 3% increase in pet reptiles in U.S. households,
corresponding to an increase in the importation of reptiles.
Reptile importation increased from 27,806 in 1986 to 798,405 in
1993 (U.S. Fish and Wildlife Service), the majority of which
were iguanas . It is estimated that 2 million pet reptiles
are owned by 2% of U.S. households, representing a substantial
increase that peaked in 1993 to 713,234 . In Canada,
Salmonellosis is estimated to affect 2.4% of the total
population each year (approximately 627,200 cases).
Salmonella marinas, S. java, S. poona, S. stanley are the
serotypes most often associated with reptiles.
Salmonellosis can also be fatal. It has been recommended that
high-risk people such as those with immature or weakened immune
systems (including babies, children younger than 5 years of age,
pregnant women, elderly people, and people with AIDS)  should
avoid contact with reptiles. Its estimated that 60% to 90% of
all reptiles carry and shed Salmonella intermittently or
continuously [7,10] because it is part of their normal microbial
flora (skin and gastrointestinal systems). It is speculated that
there is no such thing as a Salmonella-free reptile ."
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