Introduction: Many studies have shown that dust mite and cat are
the most common indoor allergies.
Cat allergy is very
common, even for people who don’t own a cat. Previous studies have shown that cat
allergen can be found in the carpets and mattresses of homes where cats are
kept but also in homes where a cat has never been present.
Research questions:
- How much cat allergen can be found in the
homes of asthmatic patients?
- How does having a cat affect the amount of
allergen found?
- Does the concentration of cat allergen in
a home affect skin allergy tests to cats?
- Does climate affect the amount of cat
allergen found in a home?
What was done: 120 adults and children with asthma participated in the study.
Participants lived in Winnipeg , Manitoba or in Vancouver ,
British Columbia
Questionnaires:
Participants answered questions about their asthma control, use of medication,
smoking habits and asthma triggers. They
were also asked if there was a cat living in the home or if they frequently
visited someone with a cat.
Home visits: Each home
was visited four times (once every season). Dust samples were collected from
the bedrooms and the mattresses using a portable vacuum cleaner and a special filter.
Skin testing: All
participants were allergy tested to 11 different environmental allergens,
including cats. Skin testing was done at
the beginning of the study.
Results:
90% of the children and
80% of the adults had allergies. Cat allergy was the most common allergy with
60% of the participants being allergic to cats. Although only 15% of the homes had one or more cats, cat allergen was found in almost all (92%) of the homes. Homes with cats had the highest amount of cat allergen.
In Winnipeg , the amount of cat allergen found in
homes without a cat was higher in winter and in spring. In Vancouver ,
the amount of cat allergen in homes without a cat was the same all year round.
The amount of cat
allergen was the same all year round in all homes that did have a cat.
The incidence of cat
allergy was the same for the participants that had a cat in the home as it was for
participants that did not have a cat in the home.
The amount of cat
allergen in the home did not seem to affect the risk of having a positive skin
test to cats.
Conclusions: It is impossible to completely avoid cat allergen. A certain amount of cat
allergen is present in almost all Canadian homes.
The amount of cat
allergen in a home can be quite high, even if the home is cat-free. Indirect
contact with a cat (visiting a friend with a cat) influences the amount of
allergen found in a cat-free home.
This may explain why
so many people with asthma develop a cat allergy even if they have never had a
cat.
Seasons only affect
the amount of cat allergen in homes that DO NOT have a cat. High concentrations
of cat allergen are present all year round if a cat lives in the home.
Having a cat free home
does not seem to prevent the development of cat allergy but it
does decrease the amount of cat allergen in the home. We still don’t know how
much cat allergen is needed to develop a cat allergy or allergic symptoms. The
amount needed to develop symptoms of asthma differs greatly from one person to
another.
It is still very
important for patients with asthma who are allergic to cats to minimize their exposure as much
as possible.
