|
Pets
and animals
|
|
|
|
Allergy
to cats
|
|
|
Symptoms
of cat allergy
|
|
|
Allergy
to other animals
|
|
|
Allergy
to feathers
|
|
|
Avoidance
|
|
|
|
|
Cats
are by far the commonest animals to cause allergy in
humans. In the UK, approximately 35% of asthmatics
are cat allergic. Dogs also cause allergy problems,
but not as commonly as cats.
However, very many
animals can and do cause allergy in those regularly
exposed to them. So those who work with
animals may present with unusual allergies!
Allergy to cats
The
main cat allergen is a protein molecule and its scientific name is Fel
d1. This protein is found mainly in the cat's
dandruff and saliva. The protein is produced in both the salivary and hair
root (sebaceous) glands. When cats lick themselves they deposit the
allergen on their fur and skin. The allergy-causing proteins (allergens)
then become airborne dust particles, and these then become inhaled into
the nose or lungs inducing allergic symptoms.
Cat allergen dust particles
are particularly light, about one tenth of the weight of dust mite
particles, and because of this they penetrate deep into the nose and
lungs, and are readily carried great distances. In comparison dog
allergen particles are much heavier, and do not travel as
widely.
Individual cats may produce more or less
of the allergen. There is unfortunately no type of cat that does not cause
allergy. Male cats may cause more allergy than female cats, because they
tend to secrete much more Fel d1.
Patients often assume
that cat allergen is only present in the houses that are homes to
cats. This is not true. Larger quantities are certainly found
in homes with cats, but homes where not cat has ever lived also contain
significant amounts of cat allergen. It is also found in offices and in
public places where cats never go. Not only is the cat allergen carried on
clothing from places with cats to other locations, people also carry cat
allergen around with them as a personal cloud.
Personal
cloud
Environmental
scientists have recently made this very interesting discovery. When humans
(and animals) move from place to place, a personal
cloud of dust particles travels around with them. So when
someone who lives in a home with a cat gets onto the bus, not only will
cat allergen particles be present on their clothing, a measurable
quantity of these electrostatically charged will be present in the personal
cloud of air they are carrying
around with them. Other people can then acquire cat allergen within their
own personal cloud simply by moving close to the cat allergen-carrying
person. So it is almost impossible to not be exposed to some level
of cat allergen. Of course, levels of exposure will be much higher where
cats are present, levels that are more likely to cause allergic symptoms.
Homes will hold cat allergen even after
a cat has been removed from the home. It can take up to six months before
levels of cat allergen in a carpeted room decrease to levels found in a
home without a cat and it can take years before cat allergen levels in
mattresses return to normal.
Symptoms of Cat Allergy
| 
|
'Hay
fever' and wheezing
Immediate rhinoconjunctivitis ('hay fever')
and wheezing (allergic asthma) on entering a
room where there is a cat. Most people with
allergies would recognise these symptoms as
being due to cat allergy. |
|
|
Delayed
symptoms
Delayed symptoms due
to cat exposure can start hours after exposure
and continue for days. Typically there may be
wheezing or a streaming nose occurring
within 1 hour; this reaction may be obvious or
it may be overlooked as being caused by
exposure to cat.
A delayed reaction
may then occur 2-12 hours later. For
example, an
asthma attack or a streaming nose may crop up
during the night following exposure to a cat,
and then recur each night, but settle down during
the day, for several days.
|
|
|
Symptoms
on re-exposure
Patients with asthma
who have cats may not realise that they are
cat allergic. Because cat dander forms
an important part of the dust around the hime,
they are exposed to cat allergen all the time,
even from their own clothing, so there is no
obvious time relationship between symptoms and
exposure to the cat..
|
Holiday
clue
It may not be until they go on holiday that
the cat owner realises their allergy to their
own cat. Symptoms
may clear up for the first time when on
holiday, only to recur dramatically within an hour or two
of returning home.
|
|
|
Contact
urticaria
Weals
or 'hives' occur on the skin where the
patient comes in contact with cat fur or
saliva.
|
|
|
Perennial
(=all year round) rhinitis
'Hay
fever' like symptoms that occur all the year round are
called perennial
rhinitis. Such symptom might
be caused or worsened by cat allergy and, if
so, allergy tests will be able to confirm this.
|
Allergy to other animals
After cats, dogs are the next most
likely animal to cause problems caused by allergy to the dust they
produce. However, this dust is not as fine as that produced by cats, and
it therefore tends not to be so readily airborne. So dogs do cause
allergy problems, but they tend not to be as severe as those cause by cats.
Apart from dogs, virtually any animal
can cause allergy, and allergists quite commonly see horse allergy, rabbit
allergy, guinea-pig allergy etc. Occasionally, a vet or zoo-worker
might present with allergy to an exotic animal and in other cases the hair
from an unexpected animal (e.g. a cow) might cause problems because its
hair has been used as a furniture or bedding filler!
 Allergy to feathers
Bird
feathers can also cause
allergy symptoms although feather allergy is suspected far more commonly
than proven. Patients who suspect they may be allergic to feathers often
prove on testing to be allergic to the dust mite,
and if their symptoms are sufficiently troublesome,
should be advised
dust mite
avoidance.
Non-feather
pillows, duvets and cushions are traditionally
advised for allergic people, regardless of whether
a feather allergy has been diagnosed. For example,
it seemed likely that down or feather fillings
would encourage dust-mite proliferation and
thereby cause more symptoms for the dust-mite
allergic patient. However, in a recent study
of dust-mite allergic patients, various types of
pillow including feather, foam and synthetic fibre
were compared. Feather pillows caused the least
problem!
Avoidance - pet
and animal allergens
Cats and dogs are by far the most likely pets
to cause problems to allergy sufferers. Cat dander is finer than dog dander,
therefore it is more likely to remain airborne and therefore cause symptoms. So
the following advice relates to coping with a cat allergy problem, although the
advice can be adapted if dog allergy is the problem.
|
|
Clean
the cat
Daily brushing (it is better if a non-allergic
person does this!) will help remove cat dander
('dandruff'). Bathing
the cat weekly to begin with, then
fortnightly, using plain warm water
significantly reduces the amount of cat
allergen produced. People who have done this
say that it is a struglle at the start,
although the cat gets to enjoy it! |
 |
|
|
Avoid
mites and fleas
Keeping the cat free from all kinds of insects
will reduce its tendency to scratch, which
will in turn reduce the amount of dander. |
|
|
Restrict
the cat
Cats should be restricted to as few rooms in
the home as possible. They should be
encouraged to spend much of their time out of
doors. |
|
|
Limit
the places where cat allergen collects
Cat dander fills the carpet pile and finds its
way into soft furnishings. Pile carpets are
better removed in favour of 'open-weave'
rugs or hard flooring. If a carpet
cannot be removed, 3% tannic acid can be
applied to the carpet and this has the effect
of making the cat allergen inert.
|
|
|
Air
filters
People with severe cat allergy who cannot
avoid living in close proximity to a cat
should consider a high efficiency (HEPA - High Efficiency Particulate Air)
air filter, particularly for the bedroom. It
is claimed that these reduce the level of airborne cat allergen by about 50%.
Although scientific studies have not
established how much benefit such air cleaners
may be, it seems likely that they will be
helpful.
|
|
|
Remove
fitted carpets
Vinyl or hardwood floors are preferable to
carpets in all situations where elements of
house dust can cause problems. This is
especially important for people allergic to
house dust mite as well as cats. Similarly,
upholstered furniture, cuddly toys, heavy
curtains and fleecy surfaces should be avoided
as much as possible
|
|
|
Encase
duvets, pillows and mattresses?
Not only are these a reservoir for the house
dust mite, they collect cat allergen as well.
Encasement in covers impermeable to both
allergens may be an advantage..
|
|
|
Ventilation
It is best to ventilate rooms where a
reduction of cat and dust allergen levels is
desired. This will both reduce humidity,
and increasing the rate of air exchange will
reduce allergen levels.
|
|
