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| Asthma - reducing your exposure to triggers |
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Written by Dr Angela Simpson, specialist registrar respiratory medicine
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Asthma is a chronic lung disease that causes sufferers
to have repeated attacks of:
-
coughing
-
wheezing
-
chest tightness
-
breathlessness.
Most people with asthma have few symptoms between attacks, but
some people have severe asthma and have symptoms all the time (chronic severe
asthma).
In people with
asthma, the linings of the air
passages (bronchi and bronchioles) are inflamed.
Some asthma sufferers have allergies. In these people, airway
inflammation occurs because they are exposed to items in their environment to
which they are allergic, for example
house dust mites,
cats and dogs. This
is known as atopic or allergic asthma.
Other people with asthma have no such allergies and the cause of
their airway inflammation is unclear (known as non-atopic asthma).
In both types of asthma, the inflamed air passages can be
irritated by lots of 'triggers'. The triggers cause the airways to
narrow, which results in an asthma attack. These triggers include:
-
viruses
-
exercise
-
cold air
-
emotion
-
pollution
-
cigarette smoke
-
substances in the workplace.
For those with allergic asthma, exposure to items to which the
person is allergic can trigger an asthma attack. These causes are also known as
allergens. However, allergens do not trigger asthma attacks in people with
non-atopic asthma.
Some people with allergies are not aware of them. If you have
asthma and think you have allergies and would be interested in allergen
avoidance, it is worth asking your GP if he can arrange for
patch testing (skin
tests) or blood tests to confirm your allergies.
Avoiding the things that trigger your asthma is only one part of
asthma management. It should be used to complement the asthma medication and
advice provided by your doctor.
Allergens
House dust mites
House dust mites are arachnids (related to spiders) and are
about 0.3mm long, so cannot be seen with the naked eye. They feed on old human
skin scales and like to live in a humid environment. They can be found in most
homes in the UK - usually anywhere that is warm, damp and collects dust, such
as:
-
pillows
-
duvets
-
mattresses
-
carpets
-
upholstered furniture.
House dust mites produce allergens, which are proteins, and
some of these are found in high concentrations in their droppings.
Many allergic asthmatics are sensitised to these proteins and
exposure to them can cause both airway inflammation and can act as a trigger
for an asthma attack. Because the mites cannot be seen but are everywhere, most
asthmatics are exposed to these allergens all the time in their homes without
realising that this exposure may be making their asthma worse.
To avoid house dust mites:
-
encase your mattress, duvet and pillows with mite-proof
bedding, which you should damp dust once a week.
Allergy UK keep
up-to-date information on cost and availability of mite-proof bedding and
vacuum cleaners.
-
wash bedding at temperatures above
55oC.
-
remove carpets in favour of smooth flooring (polished wood or
cushion floor/vinyl).
-
use a vacuum cleaner containing a high efficiency particulate
air filter (HEPA) filters and double thickness bags.
-
place children's soft toys in the freezer overnight to
kill mites and then wash them thoroughly to remove the allergen.
At night, in bed, we spend on average eight hours in close
contact with large amounts of house dust mite allergen. Measures to reduce
exposure to the allergen in bed are probably the most important.
Although vacuum cleaners that do not contain filters and
double thickness bags can remove mite allergens from carpets, they should not
be used by people with asthma. This is because they tend to release the mite
allergens into the air, and make an asthmatic person more likely to have an
asthma attack.
Sensitised patients should use vacuum cleaners with built-in
HEPA filters and double thickness bags, and ensure they service the vacuum
cleaner regularly.
Reducing humidity in the home has not been shown to be
effective in the treatment of asthma in the UK, but may work in countries with
different climates.
Killing house dust mites with chemicals (acaricides) or by
freezing them with liquid nitrogen works in the laboratory, but has not been
shown convincingly to improve asthma symptoms when it is used in the home.
Acrosan is the most commonly used acaricide and
Allergy UK will be
able to give information on where it is available.
Pets
Many asthmatics are allergic to the furred pets that they
keep, particularly
cats and dogs. Pets
shed allergen with their fur and dander and, before long, it is spread all
around the house.
The presence of the pet in the house can be both a cause of
the airway inflammation and a trigger to asthma attacks. The best way to deal
with this problem is to remove the pet, but even after the pet has gone and the
house has been thoroughly cleaned, it can be many months before the levels of
allergen return to those found in homes without pets.
For those who insist upon keeping a pet, some measures have
been shown to reduce the levels of pet allergen in the home and some evidence
has been collected to show that this may be of benefit in
asthma. These measures include:
-
washing the pet (twice a week for dogs).
-
using a vacuum cleaner with HEPA filters and double thickness
bags.
-
using an electric HEPA air filter in the bedroom and living
room that runs continuously. Make sure that you change the filters regularly.
-
remove carpets.
-
castrate male cats or get a female cat.
Food
Many people believe they are allergic to certain foods, but
true food allergies are relatively rare and affect about 5 per cent of children
and 1 per cent of adults. Some people with asthma are allergic to foods such
as:
-
fish
-
shellfish
-
nuts
-
fruit.
As the symptoms of the allergy generally start very soon after
eating the food, and are often severe, the person makes the connection and then
takes appropriate steps to avoid the food. It is often helpful for someone like
this to see an allergist, so that:
-
the allergy can be confirmed with skin prick tests or blood
tests.
-
appropriate advice on what to do if the food is eaten by
accident can be given.
In some patients with chronic, severe asthma, some foods may
exacerbate the condition, but identifying the culprits can be difficult. In
severe cases, people may be admitted to hospital for an exclusion diet (eating
only a few very simple foods), to see if this improves their asthma.
Thereafter, foods are gradually reintroduced to identify the agents that cause
the asthma to get worse. Foods such as milk, eggs and wheat are sometimes
associated with this type of allergy.
Pollen
Some asthmatics notice a worsening of their symptoms in the
pollen season, usually from March to September. Grass and tree pollens are also
difficult to avoid, but the following measures may be helpful in some
cases:
-
keeping windows shut.
-
travelling in cars with pollen filters.
-
avoiding open grassy places in the early evening.
-
checking pollen counts in the media. Pollen counts tend to be
lower by the sea.
The workplace
Some people with asthma are exposed to substances at work that
make their asthma worse; this is known as 'work-exacerbated asthma'.
Others develop asthma because of exposure to substances at work, usually within
the first few months or years of employment ('occupational asthma' or
'work-induced asthma').
It is important to recognise occupational asthma
because:
-
the best treatment for this disease is to avoid the substance
in the workplace that is causing the asthma.
-
continued exposure can make the asthma worse.
In general, for occupational asthma, the shorter the duration
of exposure to the substance, the better the chance of a full recovery.
Occupational asthma can sometimes be difficult to diagnose and may require help
and advice from an expert in occupational respiratory medicine.
The jobs that are most commonly associated with occupational
asthma are:
-
spray painting (di-isocyanates)
-
bakers (flour and enzymes)
-
soap powder manufacturing (biological enzymes)
-
healthcare workers (latex gloves)
-
plastics assembly (cyanoacrylate glues)
-
precious metal refining (platinum salts)
-
laboratory work (rats and mice)
-
electronic assembly (solder fumes).
Many other substances can cause occupational asthma, but the
vast majority of people doing these jobs will not get asthma. Treatment of
occupational asthma depends upon the specific job. Changes in the work
practice, work environment or the job itself, may be needed to avoid
exposure.
Non-specific allergens
Exercise
Many people with asthma find that exercise triggers their
asthma symptoms. Nobody knows for certain why this is. It may be because the
amount of air going in and out of the lungs increases during exercise, thereby
causing cooling and drying of the airways, which then triggers asthma symptoms.
It is important, however, that people with asthma continue to exercise and keep
fit and most people with asthma should be capable of normal activities.
You should discuss your exercise programme with your doctor or
nurse when your asthma management plan is prepared. It may be that taking your
'reliever' inhaler before exercise will be enough to help with your
symptoms. Some people who take regular exercise, or plan to increase their
exercise programme, may require an increase in the dose of their preventer
medicine.
For more information read the factsheet about
asthma on
exercise.
Viruses
Viruses cannot generally be avoided and many patients with
asthma will experience an exacerbation of their symptoms when they get a cold,
which may last for a few weeks.
Asthma patients should take particular care to check their
peak flow when they get a cold and use this information to follow their asthma
management plan. This will often involve a doubling in the dose of the inhaled
steroid (preventer inhaler) for several weeks, as the symptoms often take a
while to settle down.
The Chief Medical Officer, who advises the government on
issues of public health, recommends that those with chronic respiratory
illness, including asthma, should have the flu vaccine each year.
Aspirin
In some patients with asthma (particularly in those with nasal
polyps) taking aspirin (eg Disprin) or related medicines called non-steroidal anti-inflammatory drugs (NSAIDs, such as ibuprofen (eg Nurofen)
or diclofenac (eg Voltarol)) could
make their asthma worse, sometimes causing a very severe attack.
The component of aspirin that can cause asthma in some people
is also found in many processed foods as well as fruits and vegetables. In a
minority of patients who are very sensitive to aspirin a strict diet may need
to be followed to improve asthma symptoms. If the doctor diagnoses
aspirin-sensitive asthma, the help of a qualified dietitian may be required to
plan your diet.
Cigarette smoking
There are many reasons why people with asthma should not
smoke.
Cigarette smoke contains many
chemicals that
irritate the airways, making all smokers more susceptible to chest infections
than non-smokers.
Cigarette smoking causes cancer and other lung diseases such
as
chronic bronchitis or
emphysema (now known as COPD - chronic obstructive pulmonary disease).
COPD is more likely to develop in asthmatics who smoke than in
non-asthmatics.
In addition, children with asthma who are exposed to
cigarette smoke at home have worse lung function and require more asthma
medication than asthmatic children who live with non-smokers.
Outdoor air pollution
Air pollution comes mainly from motor vehicle exhausts, power
stations and industrial plants and factories. It is composed of ozone and
oxides of nitrogen and sulphur.
Although there is little evidence that air pollution causes
asthma, exposure to air pollution does make asthma symptoms worse for many
sufferers. Pollution, however, is difficult to avoid.
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Last updated 01.08.2005
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