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Reviewed by Dr Paul Klenerman, specialist and Professor Brian Lipworth, professor of allergies and respiratory medicine
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What is a pet allergy?
The proteins from the hair, saliva or urine of household pets
cause an allergic reaction that attacks the eyes and the airways, like hay
fever, and can result in
asthmatic symptoms.
It may also cause
atopic dermatitis or
a
nettle
rash.
It is often difficult to avoid the
allergens that can come from other
people's pets or be transported by people who have been in contact with
animals. School classes can be overloaded with pet allergens.
Most often the allergies are to cats or dogs, but rats, mice,
guinea pigs, hamsters, pet birds, horses, cows or poultry can be
involved.
Why are we allergic to pets?
Pet allergens are proteins, which when in contact with the skin
or breathed in, cause an allergic reaction that provokes the body into
producing histamine.
The histamine produces swelling and irritation of the upper
airways and causes typical hay fever and asthmatic symptoms. The tendency
toward allergic reactions is often hereditary.
People who have had
asthmatic bronchitis
as children in a household with pets, especially a cat, are at a high risk of
developing allergies towards cats as they get older.
Pets are very important in modern life. When moving house or
flat, the chances of the former owners having had a pet are high. It may take
months, and in a modern insulated flat years, before the level of allergens are
so low that an allergic reaction is not a possibility.
If pet allergies are suspected, the new house owner should try
to stay away from home for a fortnight to see whether the symptoms disappear. A
doctor or specialist could be asked to conduct an allergy test to confirm the
diagnosis.
What are the signs of pet allergy?
When touching the fur or feathers of pets; objects containing
pet allergens; or breathing in pet allergens; the following reactions may
result:
-
hay fever (seasonal
allergic rhinitis). Sneezing and a running or blocked nose.
-
eye symptoms such as
itching and watering eyes.
-
asthma. Coughing and
wheezing. (Children with
asthma).
-
children's
eczema. Itchy skin disease with red patches.
-
nettle rash. An itchy
reddish rash.
What makes the symptoms worse?
-
Polluted air,
tobacco smoke and car
fumes may precipitate asthma.
-
Any other allergens in the environment (eg pollens).
How does the doctor make the diagnosis?
Often it is enough for the doctor to know when and where the
patient got their symptoms. Skin tests and
blood samples can
confirm the diagnosis.
What should I do?
If you have allergic symptoms, you should avoid things that
provoke them and it is advisable to ensure that in your house:
-
there are no pets.
-
there are as few pieces of furniture as possible.
-
the walls, wood and floors are as clean as possible. The floor
should be polished. If necessary clean the walls, woodwork and floors
regularly.
-
only carpets that can be cleaned every week are used.
-
only sheets that can be washed regularly, like cotton sheets,
washable mattresses and synthetic blankets and pillows should be used. Do not
use woolen or cotton blankets.
-
only plastic or wooden chairs should be used . Do not have
upholstered furniture.
-
hang plastic curtains if possible. Dust them every
day.
-
use moist rags and a vacuum cleaner that has a vortex with no
bag and an allergen filter to clean the house thoroughly, at least twice a
week.
-
avoid objects that attract dust like teddy bears, pillows,
dried flowers, bric-a-brac and toys.
What else can I do?
-
Do not touch objects that are very dusty, such as books and old
clothes.
-
If you are exposed to allergy provoking elements you should
wear a mask. Even better, make people without allergies do the
cleaning!
-
Do not allow
smoking in your
house.
But what if I still want pets?
You have to be aware that there is a huge possibility that you
may have to find another home for your pet. If you are in this situation, you
should contact the RSPCA and ask them for advice.
There are low allergen producing animals, such as furless cats,
which may sometimes be OK. (But you may be allergic to cat spit and not cat
fur? If you want a black and white cat to stroke, how much fun is a cat without
fur?)
You should still decorate your house as mentioned above. Even if
the animal is only visiting you so that you can check if you are able to live
with it, it may still take half a year or more before you develop symptoms.
Dogs and cats should be bathed at least once a month in plain
water. Remember to dry the animals properly afterwards. It has been proved that
a monthly 'cat wash' lowers the level of allergens in the
house.
But what about fish or turtles? This may sometimes work but then
you may be allergic to the food they eat.
Rabbits and guinea pigs do not produce so much hair but their
urine may cause trouble. They should not live in the house but outside and be
cared for by a person without allergies.
It is possible to buy anti-allergen filters and special air
filtering systems (HEPA). Talk to your doctor or an organization for patients
with asthma or allergies before you buy these devices.
Keep animals out of bedrooms and public rooms. It would be
preferable to keep them outside of the house.
Every time you touch a pet, wash your hands thoroughly.
What complications are possible?
-
Greater susceptibility to other illnesses of the
airways.
-
Ear infections.
-
Difficulties sleeping and insomnia.
-
Worsening of asthma, and maybe even the possibility of a severe
asthma attack.
What are my prospects?
Pet owners should know it is important to avoid their allergens
because of the increase in the risk of developing, or worsening, asthma. The
symptoms can be controlled with medication but the allergy itself cannot be
removed.
For people who have only one allergy, it may be possible to have
a tolerance treatment. This desensitisation treatment is a vaccination against
the allergen. Exposure to the allergens several times in a period of up to five
years will be necessary.
What medication is given?
-
Antihistamine tablets or syrup (eg
loratadine, cetirizine, chlorphenamine). These
lessen the allergic reaction by blocking the actions of histamine. They relieve
hayfever type symptoms.
-
Nasal sprays or drops containing
sodium
cromoglicate, corticosteroids (eg beclometasone) or antihistamines (eg
levocabastine) can
be used to reduce nasal inflammation and control symptoms in the
nose.
-
Eye drops containing
sodium
cromoglicate, nedocromil, or
antihistamines (eg azelastine) reduce
eye inflammation and can be used if eye symptoms are a particular problem.
If the allergy causes asthmatic symptoms, some of the asthma
medication below may be used
-
Relievers (bronchodilators): these are
quick-acting medicines that relax the muscles of the airways. They are used
when required to relieve shortness of breath.
-
Preventers (anti-inflammatories): these act over a longer time
and work by reducing the inflammation within the airways. They should be used
regularly for maximum benefit. When the dosage and type of preventive medicine
is correct, there will be little need for reliever medicines.
Relievers
There are three groups of these.
Beta-2 agonists
These medicines cause the airways to relax and widen.
Examples of those which act for a short time (3 or 4 hours following a single
dose) are
salbutamol (eg Ventolin)
and
terbutaline (eg Bricanyl). These
medicines are inhaled from a variety of delivery devices, the most familiar
being the pressurised metered-dose-inhaler (MDI). When inhaled, these types of
medicines work within minutes to open the airways, making breathing
easier.
Longer-acting beta-2 agonists include
salmeterol (Serevent)
and
formoterol (eg Foradil,
Oxis). Their
action lasts over 12 hours, making them suitable for twice daily dosage to keep
the airways open.
Anticholinergics
One of the ways in which the size of the airways is
naturally controlled is through nerves that connect to the muscles surrounding
the airways. The nerve impulses cause the muscles to contract, thus narrowing
the airway. Anticholinergic medicines such as ipratropium bromide (Atrovent)
block this effect, allowing the airways
to open. The size of this effect is fairly small, so it is most noticeable if
the airways have already been narrowed by other conditions, such as
chronic bronchitis.
Theophylline and aminophylline
These medicines are given by mouth and are less commonly
used in Britain because they are more likely to produce side effects than
inhaled treatment. They are still in very wide use throughout the world. All
three types of bronchodilator can be combined if necessary.
Preventers
There are three main groups of these.
Corticosteroids
Corticosteroids (or 'steroids') work to reduce
the amount of inflammation within the airways, reducing their tendency to
contract. They are usually given as inhaled treatment, although sometimes oral
steroid tablets may be required for severe attacks. Although steroids are
powerful medicines with many potential side effects their safety in asthma has
been well established. It is also important to balance the problems that arise
from poorly treated asthma against the improvement in health which occurs when
the condition is well treated.
Cromones
There are two medicines in this group:
sodium
cromoglicate and
nedocromil. They
also act to reduce inflammation of the airways. They tend to be best for mild
asthma symptoms and are more effective in children than adults. The medicines
are given by inhalation and are usually very well tolerated.
Leukotriene receptor antagonists
Leukotrienes are compounds released by inflammatory cells
within the lungs and which have a powerful constricting effect upon the
airways. By blocking this effect with these antagonist medicines the
constriction is reversed. There are two such medicines currently available:
montelukast (Singulair)
and
zafirlukast (Accolate).
Most cases of allergic asthma are best controlled with an
inhaled
corticosteroid, eg
beclometasone,
which is taken at regular intervals as a preventative measure. A beta-2
agonist, eg salbutamol, is used in conjunction with this to relieve symptoms
when necessary. For patients who have associated perennial or seasonal allergic
rhinitis the use of an antihistimine, eg cetirizine, is often useful.
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Based on a text by Dr Flemming Andersen
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Last updated 16.02.2005
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