476 of these children. The researchers measured levels of cockroach, dust mite and cat
allergens in the children’s homes, and determined with allergy skin tests that 37 percent of the children were allergic to
cockroaches, 35 percent to dust mites, and 23- percent to cats. The investigators then assessed the severity of the
children’s asthma over 12 months.
They found that children who were both allergic to cockroaches and exposed to high cockroach allergen levels were
hospitalised for their asthma 3.3 times more often than children who were allergic but not exposed to high levels of
cockroach allergen, or children who were exposed to high levels of cockroach allergen but who were not allergic. Children
who were both allergic and heavily exposed to cockroach allergen also missed school more often, needed nearly twice
as many unscheduled asthma-related medical visits, and suffered through more nights with lost sleep.
In addition, the activities of the adults who cared for these children were frequently disrupted. Researchers also collected
dust samples from each child’s bedroom with a hand-held vacuum cleaner to measure the level of each allergen. While
most bedrooms had detectable levels of all allergens, 50.2% contained high disease-inducing levels of cockroach allergen
compared with 12.6% of rooms with high levels of cat allergen and 9.7% with high dust-mite allergen levels.
Even when families do all the right things at home, though, “…the biggest cockroach problem, in some cases, is at the
schools themselves,” says Dr Jean Hanley-Lopez, Los Angeles Breathmobile Director. “In inner-city L.A. schools, students
have a high level of cockroach exposure,” she says, “but I’m sure the school district is not even aware how big a problem
this is for students with asthma.”
Dr. Thomas Platts-Mills, one of the NIAID researchers, mentions several difficulties. “People don’t always understand that
they have cockroach allergies. Cockroach dust also disperses ‘all over the house,’ making it difficult to eliminate. Sprays
make a lot of asthma patients worse,” Platts-Mills adds, “and you can use all the bait traps you want, but they won’t work
if the cockroaches have a supply of food.”
“It’s all very well to have ambitions to decrease cockroaches,” he concludes, “but we need more understanding of how
to do it.” Dr. Richard Evans, an asthma specialist at Children’s Memorial Hospital in Chicago agrees: “The one thing I
would do is help people get rid of cockroaches.”
Dust mite allergy is an allergy to a microscopic organism that lives in the dust that is found in all domestic dwellings and
places of work. People are slowly recognising that dust mites and their droppings are perhaps the most common cause
of asthma and allergic rhinitis.
House dust is not a single substance but a cocktail of potentially allergenic materials. It may contain fibres from different
types of fabrics, feathers and other stuffing materials, dander from cats, dogs and other animals, bacteria, mold spores,
bits of plants and insects and other particles peculiar to an individual building. House dust also contains thousands of
microscopic mites which live in bedding, upholstered furniture, carpets etc. They thrive in summer and tend to die in
winter. However, in warm, humid environments such as a centrally-heated house, hospital or office, they continue to
thrive.
Each mite produces about twenty waste pellets a day, each containing a small amount of one of the most dangerous
chemicals known to science. Not only is the allergen of the house dust mite the usual cause of babies and small children
becoming asthmatic, it is also the commonest on a long list of irritants which cause existing asthmatics to have respiratory
symptoms.The constant presence of house dust mite droppings in the air inside homes keeps the lungs of asthmatics sensitive to
all the other factors which trigger asthmatic symptoms. If sufferers can avoid the dust mite allergen for a few months, then
usually the other factors lose much of their power.
Because mites are so tiny, their body water regulation is critical. As a result, the droppings they produce are very dry. The
average population per gram of dust is believed to be from 100 to 500, but can be up in the thousands. Egg-laying female
mites can increase the population by 25 to 30 every three weeks. Mites are equipped with sticky pads on the ends of their
feet, so they are able to burrow deep in carpet fibres and furniture where they hang on and are able to survive vacuuming.
Proteins in the dust mite droppings, called Der P1 and Der F1, are severe instigators of allergic response. When these
floating pellets are inhaled, they cause problems in the mite-allergic person.
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